The FlakHT doesn't need direct buffs per se.
However, it does suffer immensely from having its projectiles collide with whatever little tree/wall/little obstacle happens to be on the way.
Sure, Most non-Centaur tanks also suffer from the safe fate. However, with other tanks, you can simply relocate to a better vantage point and fire away. However, the FlakHT has to stop and setup. That makes it very awkward to use. It would be nice if they could make the FlakHT more consistent (e.g., more accurate, but less suppression-per-volley).
With the upcoming balance patch, I don't see the point of ever buying a FlakHT, when I can buy the cheapest MG in the game.
(With every other faction in the game, I would definitely buy the AA HT for its AA capabilities. However, for OKW, that point is moot, since they get free-popcap AA with their T4).
Flak ht doesn't need any buff, because it already does great vs infantry and is super awesome vs aircrafts, have you ever seen how it instant shoot down the p47 or how it instant pin infantry?! just think about how much it costs! and how fast it can come out and all the vet bonus and how it scales up for the late game and how it renders any enemy air ability absolutely useless! it's a great unit already
of the three aaht in game, the okw aaht have the least mobility. It should have the best firepower of the three.
Its capability against infantry is also not enough considering its downside and the building its in. As Smith also mention, the AAHT's suppression ability is not going to be enough if the okw is going to get mg as well.