Actually, what about three or four weapons?
There are automatic cannons or heavy machine guns out there designed to be dual feed -- the M242 Bushmaster 25mm cannon on the M2/M3 bradley is dual feed -- one side is the AP Sabot belt, the other side is the HE/FRAG belt; so you can have multiple ammo types without having to unload the cannon.
So figure a dual feed cannon and a pair of single shot rocket launchers on the side of a HWP; and you have a big package of flexible firepower at your fingertips.