The problem apply to all criticals.
We are now thinking of only the max you can obtain on a table, but what about the value just before that? I.e. 174 or 173?
Fundamentally, the way criticals are designed is not taking into consideration the attack roll. They are disjointed.
Simple solution:
add the concussion hit to the critical roll. This also make sense as high concussion, can represent a more dangerous hit overall.
This would also make a better solution rather than adding composite criticals (F, G, ...) that have never been something elegant, cumbersome, slow and not immune to roll low on them anyway.
Lethality goes up, but this could be an opportunity to review the criticals and make them something more progressive.
There is a lot of duplicates across the A-E tables, lethality wise, that could be improved.