Since you are obviously handy, and skilled,, rent some scafolding and put up a block chimney with a terracotta clay liner,, 8"x8" id, and install a nice stove on the wall opposite the open wall.. it looks like a natural spot.. the money saved by not buying the direct or power vent will go towards amost all the materials,, and you provide the labor.. I put up my own chimney,, it wasn't too bad,,
But, even though you have a pretty large house,, it is new, and probably well insulated and with good windows.. I think it is heatable with the keystoker, if the keystoker is putting out it's heat [not clogged with flyash] and you can move the air around better...
OK,, my position is clear,,