This would be a interesting rule to add, it has it's pros and cons imo.
Having this suggestion added on the server would allow users who are new to deathrun gain levels easier and might influence users to play on servers longer to level up. It would also allow experienced players who need to gain 3k xp (for example) to level up easier too.
The downside of this would be the fact that it could influence a whole new group of rule-breakers, we'd have to warn people who AFK for over the set number of rounds for xp farming and add new rules purely for this. This could also upset the current deathrun player-base as they've earned their levels without any automatic xp gain.
I personally think that the cons out rule the pros, so that's why im not going to support this!