Well, we already have the SdKfz 251/1-II, but theres more variants that could be added, and would get the poor thing some more use in the game.
I would like to request the:
SdKfz 251/9 "Stummel" (stump): Basicly just an SdKfz 251 with the front MG turret removed, and a low velocity 75mm KwK 37 mounted in its place. It probably wouldn't be used much (or even at all, really) outside of EW, but it would give us a vehicle similar to the M3(75) for the Axis.
SdKfz 251/10: The same as the /9, but with a 37mm Pak 36 instead of the 75mm KwK 37. If we ever get around to adding more EW tanks, it would be more usefull than the 75mm in the EW areana as far as anti-tank work goes, mostly because of the flatter trajectory and higher rate of fire.
SdKfz 251/21: An SdKfz 251 3 20mm Mg151/20's mounted back. It would give us something inbetween a Wirblewind and an M16, which would be quite interesting. The armor of an M3, Speed inbetween the two, and almost the same firepowr as the Wirblewind, and all packaged up into a smaller vehicle.
SdKfz 251/22 Same as the 251/9 and /10, but mounting the more powerfull Pak 40 L'46 in its place. This would be probably the most used variant, as it provides good firepower, and decent speed in small easy to conceal profile. This wouldn't make too bad of a tank destroyer if used properly; I could easily picture high velocity rounds from inside an undestroyed barn slamming into the side of a Tiger.
The best part is that we essentially already have 3 of these guns in the game. The 75mm L'24, the 20mm, and the Pak 40 was identicle to the KwK 40 in terms of preformance. The way I see it, we would need at least two vehicles if we add all of these, 3 depending on which ones would be added, and when the cut-off date for EW is.
Ideally, we would see an EW version, a MW/LW version, and a 251/21.
If we don't want to have 3 different guns on 1 vehicle (251/9, /10, and /22), and the 251/22 DOES makes it into EW arena, then we could just drop the 251/9. But if it doesn't, the 251/9 would be nice to have for the firepower of the 75mm in EW.