MIDI NRPN
keepalive channels per backend?
mm_backend_start might get some arguments so they don't have to fetch them all the time
mm_channel_resolver might get additional info about the mapping direction
Note source in channel value struct
Optimize core channel search (store backend offset)
Printing backend / Verbose mode

mm_managed_fd.impl is not freed currently

rtpmidi mode=peer
	mode=initiator