Quite possible, but some allowances would need to be made.
I'd go with one sound box, large like a jumbo guitar but perhaps fitted with a wedge shape (a la Manzer) and rolled arm rest and waist (a la Laskin) to make it more comfortable.
A 12 fret neck with or without a cutaway, and light weight and mini tuning machines with wood buttons would improve the balance (see a Stewart MacDonald catalogue/website). The 12 fret neck would also move the bridge back to a wider part of the top plate, for perhaps some sonic advantage.
Though a fan fret system would improve the scale length for the lower strings, it might be too radical...I think I'd try it. Double truss like the old Guild 12 strings, or single truss and a laminate neck (my preference) and an ebony fretboard for the fretlessnesslike (to coin a term) feel.
Go with wood which would react well to the wide range of timbres (how's that for a double pun?) like koa, maple, or rosewood back and sides, and spruce for the top unless koa would make the top stiffer (ask your friendly neighbourhood luthier).
I don't think any radical bracing is in order, a typical X brace would work, though you might want to research the bracing on some of the available 8 to 11 string classical guitars which appear now and again.
I'd go with hard tension high strings for the classical portion of the instrument and lighter bass strings. I really like the nylon tape wound (over steel or stainless, from Fender and LaBella) bass strings for fretless and fretted bass. Check out one of the online string guage/scale length charts to sort out guages.