At the very least, it'd need to be a mod that'd allow for other lower-level modders to come in, make their own compatible scripts that run dependent on the NPC Follower mod, and implement their own custom follower NPCs into the game.
The custom scripts that people could make would need to account for parameters such as...
- stat parameters
- primary, major, minor, misc. skills
- spell lists
- advantages
- disadvantages
- weapons
- equipment
- character sprites
NPC Followers should also probably have their own health and mana bar GUI too that's visible above their character sprite. That way, you can know when to heal them if they're getting low of health, or you can rest in order to restore their mana. Normally i'd also suggest giving them a stamina bar, but i don't exactly like the idea of an NPC follower dying out of nowhere from exhaustion, so I'd maybe suggest that as a toggle feature in the base mod. Assigning roles for custom NPCs (stuff like healer, tank, dps, etc.) should also probably be a toggle feature in the NPC Follower Mod itself if it isn't going to be an assigned parameter in the custom scripts.
On top of all that (like, as a bonus in case the modder really feels like going above and beyond when making this), it'd be cool if the parameters for the NPC Follower Mod could allow for modders to be able to write backstories and other custom dialog which can be viewed in-game through the implementation of a Follower NPC dialog menu, similar to most town NPCs in Daggerfall. It'd also be fun if the max amount of followers you could bring with you didn't have to just be 1. There's a mod i use on Skyrim that allows me to have up to 3 followers with me at a time, and it's made dungeon crawling so much fun in that game. Something like that would really suit a game like Daggerfall where the dungeons are big and the combat can be hard as balls.
(All this stuff would need to be handled by the parent mod)
Anyways, i hope that even if this idea doesn't get picked up entirely, this post ends up inspiring some people to make some more cool mods that everyone can enjoy! I absolutely love the ideas and mods that other people have come up with so far on this site.