There is a huge cost associated with trying to use the (static) Flak Regiments as a combat SU.
1. Each requires 1000 vehicle. OMG!
2. Each requires as much supplies as 1/2 a full infantry division per turn.
3. The German production system will not be able to replace excessive 88mm losses.
IMO, there should be no house rule against making stupid decisions - like assigning static Flak Regiments as SUs. Knock yourself out.
Here is another example using them. Hardly OP. Have yet to see them shred anything.

- FlakRegiment2.JPG (206.21 KiB) Viewed 562 times