I would like to suggest the Steyr 2000a with the 3 cm Mk 103/38 Flak.
It would play like a mix of the russian GAZ-MM (72-K) and ZiS-12 (94-K) or the japan Type 94, because it is mobile fast and has a fast fireing highpower Autocannon, the beloved 30mm MK 103.
I would love to see it in game, because Germany doesnt have yet a full truck AA (or full truck at all to begin with) that is fast and the Mk 103 can first be found at 6.7 on the Kugelblitz, which is high and the guns are in an unique turret not in a stylish Flak 38 common mound. The Gun will be certainly powerful against air and ground with a wide array of ammo (it could be more than currently in game, read below) of Pzgr and Sprgren.
If modeled correctly in game it will be able to shoot forwards, on the close up pictures are the wood wall to the driver visible with metal pipes to protect the head, going by the height the gun is high enove to shoot forwards over the heads of the driver (and possible 2nd person in the front) unlike the drawings show and the piping isnt made into the models, on the whole picture with the destroyed ones it is gone, but you can go by the last remaining big wooden wall with 2 horizontal boards on it which is as tall as the one to the driver and the pipes go over the wooden wall. Because of the design of the mounting you can see from the center of the round mountings on which height the barrle will be horizontal.
The mounting is with 2 cm flak allready in game on the Flakpanzer I and Flakpanzer 38, so a crew of 2 (more cant sit at the gun) can be expected, but because the only armor is the gunshield, it can perhaps get a crew of 3 with 2 sitting at the front (driver and person (commander perhaps) next to him).
It is sayed that the 3 cm Flak 103/38 (Its simply a Mk 103 gun mounted in an modified 2cm Flak 38 Mount, beltfed from 50-60 round boxes) was mounted on Sd.Kfz 70 (of which i couldnt find any pic) and on the Steyr 2000A of wich i could find a closeup of the mounted gun and a wide picture of multiple sadly allready burned out trucks.
Its place in game would perhaps be around 3.0 (similar to the ZiS-12 (94-K) and befor the CCKW 353 AA)
The story behind it is pretty unknown, but it is one of those last ditch hopes of the germans in the later stages of the war, were they lost pretty much the whole sky, so they even use the preciouse 3 cm cannons (when no plane was ready anyway) and mount it on a vehicle to protect the following infantry or other vehicles from airattecks.
The Truck is the Steyr 2000A its a more or less normal 4x4 truck
Wheelbase: 3250 mm
Track: 1458 mm at front,
1572 mm at rear
Length x with x height
5080 x 1850 x 2100
Ground clearance: 280 mm
Turning radius: 6,5 m
Max, graient 70% (35°)
Engine: Porsche Type 145 3,5 liter OHV V8 engine
Weight: 2,5 ton
The gun is the 30mm Mk 103 450 r/min and 50-60 round boxes, beltfed (perhaps 6 sec reload (Kugelblitz has 13 sec reload stock)) and somehwere of 500-600 rounds reserve.
It feature multiple different rounds:
The ones that are allready in game the Pzbrgr., Pzgr-H and the Mingengeschoss which are effective and usefull.
Pzbrgr: 30mm 0,5kg 800m/s 0g filler 58mm pen.
Pzgr-H: 30mm 0,36kg 960m/s 0g filler 77mm pen
Minengeschoss: 30mm 0,33kg 920m/s 70g HTA (84g) 4 mm
But there are more rounds, which are Usefull, one way or the other:
Allready in game but only 2mm because bugged.
Pzbrsprgr L.Spur: 30mm 0,455kg 800m/s 5g Nitropenta (8,5g) 58mm pen (ApIHeCBC)
Pzsprgr. L´Spur: 30mm 0,5 kg 800m/s 14g Pent ( 23,8g aquivalent) and 58 mm at 10m
(it is the same round as the Pzbrgr in game, but instead of Thermite it has a Pent filling and a bottom fuze instead of the Bottom screw, the round itself and the amount of steel is the same)(if you want to know how good that round would be, check protection analasys, the 3,7 cm Pzgr 18 has 13g pent (1 g less) and at 0m 47mm pen which is the same as this round has at 500m)
Sprgr L`Spur: 30mm 0,45 kg 800M/s 27g Pent (45,9g quivalent)
Usefull because it has the same ballisitcs as the Ap Ammo.
Source: Steyr 1500A in detail (Red Special Museum Line №9)
Handbuch der Flugzeugbordmunition 1936-1945
Captured Ammunition Bulletin No. 5