I would like to suggest the 10,5 cm LeFH 18/40/1 (Sf.) auf 3t Zgkw, a cheaper alternative to the other Geschützwagen and Waffenträger, beeing pretty much a 10,5 cm LeFH 18/40 on an armored halftrack, the Sd.Kfz. 11.
In 1943 the lack of SPGs was still aparent and alternatives for easy and fast production were searched.
The vehicle was one of them, having 1 prototype finished on the 27. Sep. 1943, presented to Hitler on the 22. Jan 1944 with 4 more of the planned 50 0-Serie beeing finnished in Jan 1945.
It would offer a mobile relativly strong gun (same as the StuH 42 allready ingame) with similar playstyle and fun like the italian Lancia 3Ro, tho with armor and the ability to shoot 360° without anything in the way.
Length: 5,80 m
Width: 2,20 m
Weight: 8100 kg
Speed: 52 kmh
The 10,5 cm LeFH 18/40 less 10 sec reload (aced) -5° to +42° and 360° traverse
30-60 rounds of Aphe, He and Heat (and by british source as well as american also Apcbc Pzgr Rot)
Pzgr. Aphe 14 kg 480 m/s 238g (304,64g aquivalent) filler 71mm/10m
Pzgr. Rot Apcbc 15,56 kg 470 m/s 250g (357,5g) 84mm/10m
F.H. Gr. He 14,81 kg 472 m/s 1,75 kg filler 22mm/all
Gr. 39 Rot Hl/B Heat 12,35 kg 495 m/s 2,53 kg filler aquivalent 100mm/all
Gr. 39 Rot Hl/C Heat 12,35 kg 495 m/s 2,53 kg filler aquivalent 115mm/all
F.H.Gr. F He 14,81 kg 540 m/s 2,21 kg filler
F.H. Gr. Nb. Smoke 14 kg 480 m/s 50g smokestuff dont expect much
German Explosive Ordanance Projectiles and Projectile Fuzes
Geschoßringbuch Band I
Merkblatt für die Munition der leichten Feldhaubitze 18
Panzer Tracts No.10 Artillerie Selbstfahrlafetten 15 cm s.I.G.33 auf Pz.Kpfw.I (ohne Aufbau) to Karl-Geraet (54 cm) by Thomas L. Jentz and Hilary L. Doyle
Dr. Nicolaus Hettler - Leichter Zugkraftwagen 3 ton and variants, Nuts & Bolts Volume 20