I have learned Leap of Homecoming at touch/group (since I am size +2 and to take others with me). Now since the level of the spell is so high, all others that I take with me gain a warping point which makes the mages in my troupe loathe to suppress their parma and come along for the ride, which is quite understandable.
If I reinvent the spell including certain people, then they don't get a warping point as we read the rules.
My question is: since I already know the spell, do I just need to generate a lab total equal to the level of the spell, or do I need to reinvent the spell from scratch to include the changes I want (just the specification of specific people in the group)?
In the spirit of the rulebook you create a completely new spell which can be designed to one of your friends. Good idea!
However if your SG is flexible he may give you a boon.
Carry him chips and coke.
As I understand, all you get from knowing a spell (similar spell that is) is a bonus of +1 for each magnitude of the known spell. You still require at least one season to reinvent the spell as with any spell creation lab activity.
The solution your looking for is to simply make it a permanent effect in an enchanted device (say a transport circle) into which you could then work the names of all those you wanted to be able to use it (with or without you). This way they wouldnt get warping, you wouldnt need to be around for them to have the travel benefit and you could work any and all arcane connections to the places you wanted the device to take people into the circle itself.
Just change the Duration to ring and Target to circle and voila, problem solved.
[Edited to add]: Do be aware (since it appears you are unsure) that whether it is a spell or an effect invested in a device, your lab total must be twice the final level of the spell/effect to do it in one season. Otherwise, you get 1 point for every level by which your lab total exceeds the spell/effect level every season until accumulated points equals final effect level and thus completion of the spell/device.
This kinda depends on how you read the rules, but I would read it as requiring a specially developed spell for each soul you want to tailor it for...
However, since this is exactly the same spell (with the tiny variation for attuning the effect to a person), you can re-invent using your labtexts... That should increase the pace of reinventing by a lot...
Edit: oh, and you also get a bonus for knowing a similar (well, equal) spell equal to it's magnitude.
Most likely your lab total will not be sufficient to invest the effect in a lesser enchanted device. Then there ist another way: Exert yourself in the lab (adding up to 14 points following the convenant rules), and make the item last for a shorter period of time. Seventy years of usage allows you to multiply your surplus by 2, seven years even by 5 and so on. Get someone of your sodales to help you in the lab - hey it is an item for them- or even several sodales, if you have a leadership score.
And don't forget to add the 10 points of the known spell (BL 35, Touch +1, Group +2) to your lab total. This way you will end up with an impressive lab total and may well invent this item in a single season.
Would you get BOTH the Lab text bonus (I forget how much this is in 5th ed) AND the Similiar spell bonus, for re-inventing a slight variation of a spell you already know, and had invented yourself? That's a lot!