I know I always come off like an asshole "

Just as far as bass goes, if your wanting to fill a room with it. Silly to go with a 10inch speaker simple as that. Fact a 15 is going to kill 10 as far as bass goes, and I dont think an extra five inches on a speaker is going to break his back.

As for mains its debatable if what is already there can handle the job of a larger show. A nice EQ in line would help dramatically with the mains as they stand, as IM sure there is a bit of volume being rolled back to deal with potential clipping and so on now. Past that thing being run balanced by default is going to give more headroom.

IM all for polishing a turd, but there are smart and stupid ways to go about it.