I have often wondered how big a gun you could fit in a Hezter or Stug type superstructure based on a universal carrier, would a 57mm be possible? The other thought is a front engined, covered APC variant with a rear ramp.
You might want to look at the Universal Carrier's big brother, the T16 for that.
The Carrier, Mortar, 3in, Aus.pattern, with its engine moved forward and a turntable on the rear for the mortar it carried was a very useful modification to the basic Universal Carrier concept but unfortunately wasn't built in any large numbers.
Now, a T16 carrier, with its engine moved forward like the Mortar Carrier and with a crew compartment in the rear, would have been a very useful vehicle IMHO. With a taller hull, with some overhead protection and a rear door/ramp, it would have made a passable APC although the inability of all the carriers to carry much armour would have prevented it being very useful.