That would seem absolutely awesome! To me anyway.
Makes sense.
Yes, I was browsing RoP:Magic to find appropriate familiar ideas, based on the box outlining suggestions for all Techs and Forms, and saw the cats as well. The Mercere's white cats seem like a good choice. Sure, Janus' best technique may very well be Rego but the black cats mentioned are more a Jerbiton thing. And even though the black cats are mentioned to be 'protectors of the home' and this sounds very much like Janus, the white cats are 'human friendly' and sound very appropriate as well. White cats seem to be Muto aligned and Janus may very well have had Puissant Muto as House Virtue had he not opted for the Munatum Magic option. His Muto score is ok and the point isn't to create 'the greatest familiar bond ever'. But given his skills in lab it is bound to be quite good anyway. The cats are listed as associated with Animal (small wonder, any animal is) and this is one of Janus' 4 best Forms anyway.
I think matters are settled; Janus is adopted by a white cat during a visit back to Harco.
If thinking sagas as tv series I can totally see a 'Familiar episode' featuring none of the magi...it sure beats a clip show anyway.
If Andreva just had a Black cat...it would be perfect lol
Then the magus or maga most skilled at Imaginem should invent a spell or device to project images and sounds of their cats' shenanigans. It may cause many of their sodales to waste time watching this instead of causing political mischief.
Okay, so Janus found a white cat of Mercere's lineage when he was back home at Harco.
RoP:M page 70 has an insert box with stats, but help me out here, please:
There are some virtues listed plus Flaws, and the note says to add two more Flaw points for balance. The section above about the specific cats have more typical V&Fs, also Qualities and Inferiorities.
There are a few Qualities listed, and noted that cats can have 10 points worth. But not balanced by Inferiorities, right?
And with these Qualities are bought some or all of the typical cat powers listed above in the text, by taking Greater- or Lesser Powers from among the 10 points?
The qualities for being a cat -animal qualities and inferiorities rather than magical ones- are not not balanced. You can leave them as they are and not worry about them.
But I can pick up to 10 points of magical qualities -likely from among the examples - balanced by inferiorities?
Which I will because u want the cat to have powers.
Can somebody suggest good names for the cat? Something signifying being a protector of his (expanded human) family and home. I'm thinking make cat, with an interest in dreading his genes like Janus has.
The ancient egyptians wrote on walls and worshipped cats. Ah, progress 
My Mercere (Patricia) has a black and white cat called Watchful/Foresightful (Jessica in her sire's mother tongue of Hebrew). Pat also has a small red cart that she trudles around in, and does her best magic at the start of the day.
Bob
Well Saoirsé's cat is named Max from Maximus/Maxima, but that might just be her transvestite cat's drag queen persona speaking... 
A magical creature gets a number of points of magical qualities equal to its might (prior to adjustment due to size). Depending upon what sort of a magical animal (such as an animal of virtue) there might be some requirements.
Thanks, things make more sense now. The text in the insert box about how the Cats have a base Might of 10 hence 10 Qualities, but due to Size they have +3 Might without this affecting the number of Qualities is now clearer to me.
Any good ideas for names?
Below are the stats for Janus' white cat of the Mercere lineage (name pending) which he intends to form an Familiar bond with during the start of the period Year +46-60. Stats are from RoP:Magic page 70 plus Book of Mundane Beasts. From the template and the suggested V&Fs I balanced him with two Flaws plus another one to get Second Sight. For the 10 points of Qualities I took a few more of the suggested Virtues plus one Greater and two Lesser Powers.
Characteristics include the improvements from 3 castings of Basuas' Intelligence booster, and respectively 2 and 4 castings of Andreva's boosters for Presence and Communication. Janus spends a great deal of vis, but he can borrow without interest from his house. I'm having him spend even more time crafting devices for sale to earn this vis spent.
Supposing I want to invent come craft magic for harvesting, which Targets seem the most sensible?
Considering the other spells of Janus affect Circles fields and orchards are round to begin with, can T:Circle simply harvest and stack in nice sheafs all the grain stalks? I'm thinking separate effect to separate the grain from the chaff and stalks. A sufficiently large Group should also doe the trick here
For vegetable gardens pulling up all the carrots or turnips should also be possible using T:Circle. I'm thinking separate effect to clean and cut the vegetables to be ready for the cook pot immediately.
For orchards with fruit trees and berry bushed the individual items need to be picked. One could go tree (or bush) by tree and pick off all fruits by T:Ind? Again, I think T:Circle should pick all of them, and put them in baskets or barrels.
For trees bearing nuts my agronomic skills are pitifully poor, but are they picked off the trees as well, or do you wait until they are done and fall off? If the first, the fruit-picking deice should do the trick. if not, a separate device picking up all nuts from the ground to put in barrels is needed.
Edit: Maybe a magical nutcracker as well?
Once fruits and berries are picked I'm thinking an effect to cook and preserve then instantly, so the workers only need to put the finished foodstuffs in clay pots and seal them. Maybe a device affecting both He and An to put a cork in the pots and seal with beeswax?
Actually, I'm also now thinking a ReTe effect to turn a lump of clay into a finished and fired pot.
Taking a cue from the "Armoire of Excess" from Through the Aegis - Collem Leonis covenant which Janus should build, he should also make a 'Linen Closet of the Wastrel' so there is a fresh supply of linen for beds every day. No need to ever wash it, but neds need to be made every day...which smells like another device.
I see a lot of Anulus Connectens' covenfolk training Finesse rather than real, practical skills :S
You harvest nuts the same way as fruit - picking them. My boyfriend is a gardener, so any Herbam related questions, he could answer 
Sorry to be a bother but...your familiar appears to turn into a person. That is kind of odd. Just thought I should mention it.
As for 'harvest targets'...I'd lean more towards Boundary than Circle, simply because I know Boundary can effect all targets within a defined space. My understanding of Circle is that it is less 'precise' and certainly more unstable, (anything crossing the circle breaks the circle).
Magically, by RAW, I don't think the distinction exists but why take chances?
No worries, no need to apologize.
It surprised me as well, but this is actually written in RoP:M about the white cats from Mercere's lineage . I could easily have avoided it, but seeing as Janus wants his Familiar to help in the lab this is actually quite useful. So the cat can use a humanoid shape to actually handle things physically and not just work in advisory capacity.
Good question though, because it is somewhat...odd?
Yes, but T:Boundary is for Rituals.
The fields, gardens and orchards are intended to be circular and bordered by a stone wall. The vulnerability is really most for D:Ring spells, which end if even a single blade of grass lands on the circle. For D:Mom T:Circle spells I don't see this is an issue. While casting you need to walk around the walled field and trace the line of the circle, and Bam! the spell is cast. Sure, statistics dictate that once in a while a bird may take a crap on the circle and the spell fizzled since there is no legal Target...But that's why this effect is intended for a device with Unlimited uses per day. Fruit not picked? Repeat as needed!
If you use loose interpretations of T:Room to encompass all enclosed spaces then the walled garden should be a legal Target as well. IIRC the description of T_Room mentions courtyards, which is really just a space bordered by buildings.
I see eight virtues (aside from true friend) and only four minor flaws
Oh yeah. I took some Supernatural Virtues in stead of some of the Qualities per the suggestions for the cat template. That's how the text made sense to me. Nothing really vital though, if I'm mistaken I can easily drop a lot of them. Supernatural Virtues with associated Supernatural Abilities are point sinks!
I'd suggest putting "minor virtue x4" in your list of supernatural qualities. That would make things clear for me if I were reading it and trying to figure out where things came from.