I've found left handed mousing is a lot nicer for numpad work recently too like yourself. Would have rather get a keyboard with the numpad on the left but I can only find DSI ones on ebay for $130+, or a really ugly one with irregular keys shapes. Just don't want to spend that much on a keyboard again.
Adapting to left handed mousing hasn't been so troubling as I thought it would be. I have the strangest sensation after using the mouse left handed though, like the whole left side of my body actually exists now whereas before it didn't.
I don't think I'd go so far as to take it into my gaming though.