I agree, the higher you can go on the ceilings, the better. A lift will not only make it easier to work on the restoration project, but easier to work on your personal vehicles as well. And you might be able to build almost like a second story, with stairs, for storage and what not.
And make sure you plan not only enough room for what you want, but enough room for what your wife will want too. Because she will try and take over at least some of it, and possibly all of it, if you let her.