In that case, it's more a matter of Schema taking the time to implement it than difficulty. Eventually it might be possible to replace block faces with models at close range, at least theoretically, but that's a bit much to be thinking about at this point. Things like chairs or modeled decorations, however, are more an issue of Schema getting around to it.
On one hand, they'd be awesome to have. On the other hand, there are probably more important things to be working on right now. Still, I certainly won't stop people from pestering him about adding chairs. :p