Still, I don't see a real problem here. So we will be back to "your first vehicle should be a Puma" thing if playing against soviets. Doesn't bother me. If you kill that M5 (and Puma can do it quickly and without pain), you will have the upper hand. Further, you can compensate the lack of AI power by building more sturmpios as usual or / and help after 3 CPs with jaeger infantry or fallschirms.
Thats kinda my point tho, flacktrack is abit of a dead unit.
Its more risk, less reward. Ive seen games lost purely because someone got one rather than a Puma or Stukka.
Like someone else said... it should be used as a support unit not an assault unit.
Which brings us back to...
OKW cannot afford 55 fuel on a unit to merely support their frontline that will be wiped out easily. If it was cheaper it may be more of an option. (more MP less fuel).