I had the idea of keeping both the classic larger sized Skirmish maps along with the newer sized ones, just like Firefight as you said has two map versions and with the new voting system I think it would work fine (if players don't like the bigger map, vote for the smaller version and vice versa).
I just hope some people stick with Skirmish after the boost ends, I love this mode! Also if you haven't tried they added Outskirts Skirmish finally and it's awesome!
I'm ashamed to admit, I wasn't playing much skirmish before the XP boost, even though I played it a lot in source insurgency. I'm glad they added the temporary XP boost, I've been having a hell of a lot of fun playing it (and of course getting some extra XP doesn't hurt either).