They could just simply change the effect of exhaustion levels to make them less violent.
The berserker subclass is OP now but there's a middle ground between OP and useless.
RAW effects are too rude for the game but, in exemple speed reduced by 2 meters, -1 on attack roll,... would be perfect trade-off.
And (extra) food to reduce exhaustion of all characters could also be interresting. Let's say they need +5 rations / level of exhaustion when they long rest. Still just an exemple.
Agree that it is OP now, but that is mainly because we are stopped at lv 4.
At lv 5, fighters, barbarians etc get an extra attack. So berserkers go from 2x the attacks of fighters to 1.5x.
And of course fighters add a lot of damage with their maneuvers, especially Riposte (which, if you build your character well, also gives you an extra attack each turn).
And of course they get extra feats so you will be able to do stuff like PAM + GWM + Sentinel etc
Berserkers do not get any strong class features after lv 3, they are really defined by frenzy...
Changing the exhaustion to not cripple Berserkers specifically would also have other downsides, as balancing usually has.
For example, how would that affect the viability of spells like Sickening Radiance?
Or how would that interact with the thing exhaustion was initially intended for, overworld travel and a lack of rests?
Honestly, I think any fix that is there because any specific class is unbalanced should only affect the class, not more broad mechanics, as that always has unintended sideeffects.
I like your idea a lot (though I would like leaving exhaustion out even more), but I still prefer exhaustion being removed on a short rest for Berserkers specifically
