youre going about it the right way in considering all the possibilities before embarking on the project. it seems you have your heart set on the project and your letting your head doubt it. where theres a will theres a way and they are not problems they are just solutions that need finding and all.
i used a different donor completely for the build and had my fair share of "solutions" to find but time and perseverance anything is possible. but like others have mentioned i can see it being alot more involved than a standard bookbuild.
whatever you decide its going to be fun !