problem with exhaustion is that id gives disadvantage to rolls.
It's a huge blow and it negates any effort to come with advantage in play.
Going from disadvantage to normal roll is not interesting or fun as going from normal roll to advantage.
My house rule is gradual penalty to everything with every exhaustion level:
-1 to all d20 rolls(checks, saves, attacks), -1 to all DCs, -5ft movement(min speed of 5ft) -1 max HP per level(min of 1 HP per HD).
so someone suffering from 4 levels of exhaustion will suffer -4 to all d20 rolls, -4 to all DCs, -20ft movement and -4 max HP per HD(I.E. 7th level character would have health reduced by 28, to a minimum of 7 HP. If you have a 7th level wizard with 8 CON and normal max HP of 23, wizard would end with 7 HP, folowing 1 HP per HD min)
now, even with -4 penalty, it is still possible to go for advantage and negate most of that penalty and use advantage for it's own mechanics(I.E. sneak attack)
You die as normal with 6 exhaustion levels.
