So here's a fun thought experiment to do.
Smash Bros games are usually pretty good at giving returning franchises new content. In particular, the far majority of franchises get new music every game, barring retros sometimes. There are only so many times you can remix the Ice Climber soundtrack, for example.
Still, some non-retro franchises didn't get ANY new music in the transition from Smash 4 to Ultimate. NOTE: I'm including anything with an emblem that isn't a hardware stage. So stage only franchises count. These franchises include...
Kid Icarus
Punch Out!!
Bayonetta
Balloon Fight
On top of that, some franchises got new tracks, but no new remixes. These franchises include...
Star Fox
Sonic
What music tracks or remixes would you add to help these franchises out?