Take a look at the diagrams and data in Panzertracts No. 15-3. After fitting in the 7.5cm and ammunition storage, there's not a lot of room for the additional radios normally found on a command vehicle. Each 251/9 was fitted with a single short-range Fu.Spr.Ger.f set and a single 2-meter antenna, for communications within the platoon.
That particular section of the Panzertracts volume is fairly unique, as it quotes at length from a 1943 pamphlet detailing the tactical employment of the gun platoon. Interesting reading, but suggests that this would be too useful and flexible an asset to turn over to a commander!
Allen