I would like to suggest the Panzerselbstfahrlafette Ia with 5 cm Pak 38 L/60.
What it is: It is a lightly armored small and nimble ammonitioncarrier modifed to mount a 5 cm Pak 38 L/60 in an unique (moveble) gunshild. The design is the counter design with preproduced parts to the E-5/Panzerkleinzerstörer. The difference between these vehicle of wich 2 were produced to the normal Gepanzerter Munitionsschlepper Vk 302 (Borgward) are the new side hatchets instead of 2 on the top and the most obvios one is the new back with the 5 cm Gun in a big shield.
It would probaply drive and play similar to the Zis-30 as it too is a tractor but even smaller than the german one i am suggesting. With haveing 14,5mm of frontal armor it would be immune to every small caliber mg but easyly pirced by everything beyond. but beeing so small and having 12,22 hp/t it would be nimble (but not fast with 30 kmph) and could easily reach nice shooting spots and hide with bushes behind bushes and small hills.
History: As mentioned above this is the counter/other designe but with preproduced parts to mobilize the 5 cm Pak 38 L/60. To be exact, overall give the Motorized Infantry and Airborn units a cheap, light and mobile anti tank gun/vehicle. Produced be Rheinmetall-Borsig a total of 2 were build with delays (2nd half of 1942) and cancelation because of the ineffectiveness of the AT gun.
The maingoal of the vehicle were to be light mobile small and packing quite a punch. With thin armor and if it was to have Vorpanzer (spaced armor) or/and also Schürzen.
The story of the basevehicle Vk (Vollketten) 301 a fully tracked armored ammo transport vehicle. Capable of carrying 500kg of storage in a bin in the back and 500 kg more in an additional trailer. This vehicle was requested in 1937 by In 6 (i forgot the full name).
But with the resulting Vk 301 wasnt the In 6 satisfied. So Borgward build based on the additional requrements the inproved new version the Vk 302. It was approved for production and Borgward instructed to build 400 vehicles but only fewer than 50 were ever build by 1944 all were lost in combat.
The change of Vk 302 to the Pz.Sfl Ia mit 5 cm Pak 38 L/60 was the removal of the storage bins (replaced with the gun and space for the crew) a new crewcompartment with doors to the sides instead of the top.
Total weight, battle-ready 4.5 tonnes
Crew 3 (Commander/Gunner, Loader, and Driver)
Propulsion Borgward 6 M 2.3 RTBV 55 hp @ 3600 rpm
Max. Road Speed 30 km/h
Operational range 200 km
Primary Armament 5 cm PaK 38 anti-tank gun 35+ rounds
Elevation -10° to +20°
Hull Armor 6.5-14.5 mm
Superstructure Armor 6-8 mm
Total Built 2 Prototypes
Sources: German Mititary Vehicles, Krause Publications D. Doyle (2005)
T.L. Jentz and H.L. Doyle (2010) Panzer Tracts No.7-1 Panzerjager
T.L. Jentz and H.L. Doyle (2009) Panzer Tracts No.17 Gepanzerte Hachshub Fahrzeuge
P. Chamberlain and H. Doyle (1978) Encyclopedia of German Tanks of World War Two – Revised Edition, Arms and Armor press.
Ian V.Hogg (1979) German Artillery of World War Two, Grenhill.