I'm a noob here so perhaps this or something close has already been suggested.
I was thinking for infill that the layer could be printed at double the thickness of the shells and then it would only have to be printed every other wall layer.
Could speed things up a little. The infill doesn't have to be anywhere near the quality of the walls so printing it twice as thick could be just fine.
While I'm thinking about it, maybe the option to print layers at changing thickness would give a different texture like look to the walls. The change might be each layer is a slightly different thickness or it might be that the thickness changes on some linear frequency within the layer. There are obvious limits to how much the thickness could vary and still print.
Anyway, just a couple wild ideas.