Been following along and a lot to take in, so if this were mentioned sorry I missed it.
Wasnt there an attempt to make cata 3d a while back using voxel, i think the name was? The developement had just stopped but if i remember right, it seemed to work quite well. I would have to search but i think the old stuff is still out there.
And as far as being tile/turn based 3d, imo it would seem that would be the best way to go and keep it like it is. Another example would be the game Simutrans, tho that is a realtime game.
Lots of ideas floating around, anyone going to take it on yet? Or this is just discussion and conjecture at the moment?