Just my opinion, but I don't think there's anything wrong with either of those 2 new rules you suggested. Stopping at the 6th gen makes the compo more inclusive in regard to skill ceiling, sound quality and VST/libraries requirements. PRC is already dedicated to lesser-known games, which means that if you went with popular VGM instead, it'd make both compos complementary rather than a challenge not to step on each others toes every round.
Bit of advice tho: if you're gonna helm any kind of community event, it is literally your job as an organizer to plan for a successful turnout. Starting with (and I've said it a few times already) advertising your compo to make sure there is participation. In the age of Discord servers, especially when contestants come from the same artist pool in a buried forum subsection, relying on the same 3 people to carry every event, year after year, isn't realistic. Everyone's interests shift, as do life's priorities and even enthusiasm has limits.