one thing to watch out for with the pioneers: It seems like any engineer type I've used for open combat has a serious rally problem. If they can stay fairly hidden, use scouts to locate unsupported tanks, hex in, blast 'em and split, they seem to do fine, but once they get pinned, you'll play hell getting them broke loose again. I've tried lots of different variations on that theme, and I'm still trying to work out the bugs
Matt