Once I thoroughly understand Lemmy's functionality through the Sublinks Re-implementation (since Rust is like Greek to me but Java I know), I want to try and put in a community tag feature that would be able to assemble a feed of communities across the Fediverse dedicated to one topic.
I may take me 6 months to a year if I commit to it, but I do think some community aggregation mechanism like that is sorely missing from Lemmy and could help distribute post load better while ensuring a userbase on non-general topics remain active.