That ACIV is obviously something they have mocked up themselves as the real ACIV had a new, wider turret.
As for using a 38(t) hull - too narrow for anything larger than a 2 Pdr. You'd need to splice in a section of new hull to make the turret ring large enough for a three man crew.
Using Panzer III components I could see working. It would be large enough to mount a 6 Pdr. Its armour would be thick enough to withstand most Japanese AT weapons. It would need more than likely a new, different turret with a higher mantlet for the 6 Pdr. It would find it difficult to have a 17 Pdr mounted in it because of the turret ring size.
A Panzer IV would be another good choice. However, castings would alter it's shape considerably. Again a higher turret would be required.
As I suggested though, neither could not be used against the Germans for obvious reasons.