The stun grenades are better than you think. They absolutely devastate infantry inside building and arguably do more damage than rifle nades.
The stun grenade in combo with another grenade can guarantee wipes on squads. Use two squads one throwing the Stun the other the regular grenade, retreating units right now still must wait for the stun to wear off and a bug sometimes cancels their retreat.
The Tiger Ace as a unit is fundamentally broken for COH2, vet is earned not given (excusing Elite and to some degree Rifle company). However, it is currently neutered to near the point of troll unit because of the income penalties. Removing it seems unlikely, it should probably cost fuel and not cut off your fuel income.