I have my XY homes set to the 0,0 on the X,Y coordinates and top of travel on the Z axis. It is just a personal preference, as I suspect a lot of set-ups are.
When I was considering CNC'ing my little Clarke CMD10 (which never happened) I thought about having a toggle switch on the centre of each of the X and Y, with spring loaded flaps to operate them. The idea was that you then had some input to say which part of the table you were on and could home accordingly to the centre.

Many great inventors start off with what other people rate as stupid ideas. My end point seems to be the stupid idea.