How about a Prowler Turret with two gunner seats?
I could run both a Walker and the nubetube-whatsitcalled for maximum flexibility, at the cost of one extra kill for that AT-mine engie and one less soldier in the Sundy.
Would be fun.
Of course, I'd much rather get a Main Cannon with it's own gunner seat, but that's a different issue.
The quad-barrel gun looks neat, I'll give them that.