Basic specs would be something like
Weight: 6 tons
Power: 63kW
Armour: 0-7mm
Height: 2.6m+
armamement: up to 2-pounder for maneuver warfare, up to short version of 18-pounder gun for mobile pillbox role
Overall, better mobility (although still slightly worse than Ha-Go), and seriously inferior to Ha-go in other aspects. Especially bad is survivability at close-range fight typical for jungle warfare.
P.S. 25-pounder gun (even with short barrel and reduced powder charge) would be impossible for Loyd carrier derived vehicle. Too strong recoil on too light chassis will either topple vehicle at low elevation or break suspension at high elevation. The 1954 year derivative of Loyd carrier - CATI 90 which had gun similar to 25-pounder was specifically designed to place gun very low and have limited elevation, so overturning torque is reduced and weak suspension is less loaded. And i am not sure if even all these tweaks have made CATI 90 to survive recoil of more than few shots.
It is common line of thought for amateur to try to fit most powerful armament to the lightest possible chassis, and generally it is wrong. Best combat efficiency is achieved with weapon which hit and barely disable target, not with weapon which produce largest crater a hundred meters off target. Also, the general efficiency of artillery against "soft" targets is reverse proportional to gun caliber.
Type 95 Ha-Go
Horsepower 120hp@1800rpm
Power/Weight Ratio 15.6 hp/t
Ground Pressure 8.9 psi
Ground Clearance (m) 0.39
Fuel Diesel
Range (km) 250
Gradient (degrees) 30-40°
Armor 12mm basis Front/Sides/Turret
Crew: 3 No Radio
Armament:
Type 98 37mm Tank Gun
Caliber : 37 mm
Barrel Length : 1.359 m (L36.7)
EL Angle of Fire : -15 to +20 Degrees
AZ Angle of Fire : 20 Degrees
Muzzle Velocity : 685 m/sec
Penetration : 25 mm/500 m
Not really a terror in the Jungle, or anywhere else
Half the battle is showing up. They showed up.
Now for SPGs
For big guns on small vehicles
7.1 ton M56 Scorpion, with a 90mm with a bit over twice the recoil energy of the 25 pdr
The T16 Universal Carrier from Canada used a Ford V8, and a bit heavier than the British around 5 tons. 105 HP, 7.4psi ground pressure