Prefab .fbx updates

I'm currently designing a game as a solo developer... I'm creating the models, animations, scripts and gameplay elements alone. I have the game to a point where network collision is working, clients view remote animations properly, position is updated properly etc...

I'm simply trying to take the basic model i created for testing purposes and replace it with a model that has new animations attached. Since i'm using prefabs, I either need to create a new prefab and replace all elements including attached weapon models and hierarchy child based scripts... or I can restart the game over so everything is custom designed for the new model (which is a more defined version of what already exists)

I'm quite frustrated at how difficult this entire process is. Is there another way to just update the model so the engine can see all my animations?

I currently have walking/idle animations. The update includes a new walking/running animation, same idle animation, a basic attack animation, and a skilled attack animation. Since I'm creating a RPG I find it quite rude to need to re-design the entire prefab just to add a few extra animations seeing as skill trees will become more in-depth and animations will increase as the amount of players increase. IE; 10 players need attacks and basic features only, 100 players will want new skills, 1000 players will want emotes and 10,000 players will want end-game bonus animations (enlightened/winged emotes)

Now i'm thinking I need to design ALL animations I will EVER want so I don't ever need to re-design the prefab to include any new animations. My model is currently not textured and may cause more future problems.

Please help... I have big plans, and am hoping to add new things every week or month. With the prefab redesign happening for every update, that may sap an entire day just to update the new prefab.