If Engine critical was to ensue one might as well change the name of the ability to "260 Suicide charge". Maybe save that for the Japs expansion.
It's not engine critical, it seems you never "failed" to ram something in order to gain a quick boost to catch up something ahead. You are a bit slower (you can still move) but you'll recover automatically over time. Amount of slow and duration could be tweaked easily. It could not affect your max speed and just acceleration, etc.
And I don't think it should be that unforgiving to go operate without support with the Tiger. It is supposed to be tough. It's not the same with the IS-2. You can "oh shit" and reverse and make it out with the IS-2 most of the time while most of the time the Tiger dies. Not right I don't think.
-TTK of pak40 and zis is equal against IS2 and Tiger. TWP is 100% chance of penetration.
-37-42% chance to pen with faust vs 33% to pen with AT nades
-PV 70-59% vs IS2. Su85 is 67-60%
-AT infantry (shrecks) 48-43% vs PTRS (?)...
It's basically the same => unsupported tank > dead tank*
*RNG god not included.