I like the idea of Exhaustion being used instead of Life Drain, but like others have suggested, it would be very deadly very quickly. Especially in the kinds of games that I run.
If I ever go that route, I would need to expand the Exhaustion Table out to 10 levels instead of 6, sort of spread all of those bad things out a bit more so that they don't pile up so quickly. Maybe add a few other things in there to pad out and "dilute" the list as well.
Something like this, maybe? Just spitballing here...
Exhaustion Level | Effect |
1 | Disadvantage on ability checks |
2 | Speed reduced by 10 |
3 | Disadvantage on attack rolls |
4 | Speed reduced by 10 |
5 | Disadvantage on save throws |
6 | Cannot take Reactions |
7 | Hit point maximum halved |
8 | ? |
9 | Speed reduced to 0 |
10 | Death (or maybe Unconscious instead?) |
But overall? I really like this idea.