Much of the confusion has been lifted from me as i have gotten to see the Seaworthy Cog spell. Much of that was based on your description which does not match the Cog spell. The wood is not created into finished pieces then put together in the Cog spell. The boat appears BAMF!! as a completed boat based on the template boat. In the above spell, Alexei will have to find his template warehouse and then make the spell which will produce an exact copy. It is not clear from the Cog spell that you need the template in the lab with you when you create the spell. i suspect that you do since they discuss lab sizes. If so then it is really really useless for what we are discussing. And a less version of Wizard's Tower would be much simpler.
If we take it as implicit, that a template is necessary for a cog, then it should be just as necessary for the tower. In short, I don't agree that a template is actually necessary in either case.
I'm just going on what that spell is based on. I've seen Wizard's Tower when a set of detailed drawings are needed to construct the tower. I would also say that a tower does not have many separate parts that a ship would have. The same as a warehouse would have far fewer parts as well. The tower could be done with a single piece of stone with no problems. Not so a complex boat.
Well, if you supply a lab text for a stone warehouse and herbam vis...Harco will be less than pleased. 
I'm explicitly saying here and now, you can create it as I indicated above. Base 3, to me doesn't make a lot of sense. But, I'll go with whatever the troupe wants. It's at best a level 30 spell
I'll defer to Alexei to see if he wants to make that spell for them. JL and I can discuss the inner workings in another thread 
Alexei can and would be fine with making the spell, just looking at Arts, he has Creo 16 and Herbam10-14, MT 6 I think, and Int +2, with Aura over 40 lab total I think. It would take 3 seasons most likely. I'd have to redo his studies for that timeframe, would we be supplying the vis as well for the first casting, and also provide a readable lab text? Just looking at the commitment of time, it looks like it'd be a year maybe.
If Alexei wants to do the ritual, and supply the text, which can then be translated at leisure. Of course, then they can translate lab texts of Alexei's at a lesser level.
And there are apprentices at Mons Electi, although I'm unsure what they are doing...
Sevrin, what is Gregario doing in the up-coming seasons? Perhaps Alexei could make use of him in the lab.
Korvin turns to Alexei when Sevrin goes to check some books Gregario was a failed apprentice 20 years ago. He is very useful in the lab and is sometimes used by my House when we have a large project.
"He's actually here, vacationing, and as far as his schedule, I'm not sure what it is. But, Instatella would make this a priority project for him."
((Whenever Alexei figures out his schedule, we'll have him arrive. He adds a +14 to LT.))
And I will lend Abigail to you for a season. She is a wonder in the lab ( LT +12)
((Just for reference, I'm a bit out of it, can we have the deal summed up just one more time? And looking at the other posts...we have HUNDREDS of pawns of vis? If everyone is fine, let's throw vis at the problem and save time!))
((At this time, you don't have hundreds, as in several hundreds. You might have a couple hundred, or close to that... But if you just want to throw pawns of Herbam at the problem, that's not all that hard to do, I don't think.))
((I made an offer on what we HAVE at this time(1223.2). If you want to wait a year to pay the other 15 rather than do the spell we can pay it. I was just trying to help out by giving options))
((as of 1223.2, it looks like we have 186 pawns of vis on hand, of which 15 is Herbam, if I have my OpenOffice spreadsheet figured right.))
((We get 2 rooks of Herbam just before Alexei would need it))
((OK, that's why I wanted to make sure. So we could pay for it, seems rather wasteful and contrary after all the work though to suddenly say 'heck with it, here's the vis'. So we'll go through as planned. I'll have to revise Alexei's time.))
((There's no work (I don't consider mine and jebrick's pratter about the spell to be work)... These are the typical choices of the summer covenant. You can pay as you'd like. Another 2 rooks comes available at the end of the year, IIRC and Alexei would know this. 5 more pawns could be paid in something else. You don't have to pay for a season, if you don't want to do it.))
((Then let's pay for it, that way we can be done and I don't have to revise a year of stuff.))
Alexei enjoys the discussion over the spell and its parameters. His Pater often said he wasn't the brightest of candles, but hard study could make up for it. So while he followed their quick exchanges he would only get the more subtle nuances later. Finally after looking over Korvin's shoulder at the vis in store, he came to a decision.
"Sodales, thank you. And I'm sorry to interrupt, but...perhaps we can just pay the vis? I sincerely hope I haven't wasted anyone's time. I have been working this issue for over a week now, and would just like it to be done. What was the price? Was it 30 pawns agreed upon and then bargaining for the remainder? How about 38 pawns total?"
Korvin will sit back and let Alexei bargain.
"Not quite... Korvin offered 30 pawns and some help with a spell to make the warehouses. My initial offer to you was 45 pawns. So, if the spell isn't part of the deal, we're starting at 45 pawns. And you're counter offer is 38. Very well, call it 40 pawns and we're done. And it must be Herbam. We need to take delivery of it as quickly as possible, if we can have it all by the Winter Solstice, or close to then..."