But since the whole xp, DP system is tied to lvls in RM it is what it is.
There were a lot of discussions on the forums about the matter and, well, when it comes to the XPs, many GMs don't go with them, merely rewarding levels every few game sessions. As such, since each level pretty much merely grants matching DPs, a GM may just hand them to his players every few game sessions. Not much rules to "rewrite".
We’ve thought about disassociating RR and spell casting from lvls but never got around to doing so.
In later RM versions (and, IIRC, as an optional rule in RM2), spell lists are developed as skill ranks, a PC's proficiency in a given spell list equalling his number of ranks in said list. There's not much to "rewrite" to consider his caster's level in the aforementioned list actually is his number of ranks as well.
It never made sense to us that things like resistance to magic or poison should be somehow based on how much xp you’ve earned rather than your stats (not sure skills would make you less likely to die from poison).
There are already in RM2 itself rules
NOT to have a poison's effects depend on a character's level (thus
NOT to depend on a RR), namely the constitution-based severity and the luck-based severity. Once again, there's nothing to "rewrite" as the rules already exist!
That only leaves the RR to resist spells, so, really, IMO, there's not much to rewrite.