I had actually thought about that exact idea, but the main issue is - what if you want to use that track on more than one level? For example, if you had a special music for the final level of each rank. You'd then have to include four copies of it. Which is why I'm thinking along the lines of sticking to the default NeoLemmix system - that is, they're titled track_##, and it simply loops them once it passes a certain one (which doesn't have to be all of them - for example, you could include up to track_08 but tell it only to go as far as 6 in the automatic rotation, with 7 and 8 being reserved for special levels), plus two tracks with specific titles "gimmick" and "frenzy" though these would not be nessecary if your pack doesn't use gimmick and/or frenzy levels. Then, in each level, there's a setting for which music number to use; whatever value is set here, it plays that track, so on the levels you want the special music, you'd just set this to 7 / 8. (To make a level just use the normal rotation of musics, just set it to 0.) Between the normal rotation and any special musics (but not including the gimmick and frenzy ones), you can have a total of up to 252 tracks in the player, which should be more than enough. The reason the limit is 252 is because the music setting can only range from 0 to 255; and setting it to any of 0 / 253 / 254 / 255 have special functions.
Since this is a fairly effective system, that's why I'm thinking the easiest thing to do would be just backport this. The downside is of course that NeoLemEdit is the only level editor that supports the setting. (Lemmix Editor won't take too kindly to levels that have it set, whereas LemEdit should load them fine but might erase the setting when you save them again, not sure.) But you can always design the level in your preferred editor, then just use NeoLemEdit to make that change.