In the spigot plugin McMMO, you level skills by using them, for example, to level mining, you just go digging into the ground.

I know it's probably a big request, as it would not just involve watching the player's every action, but also balancing each action for the skill amount given. Some stats could be taken from McMMO for that, but balancing with this mod's abilities would still be a problem to address. But this is the best McMMO replacement mod I can find, it looks great, I just don't want another thing encouraging my server modpack's players to rely on mob farms if I can avoid it.

This will probably be included as a part of the 1.13 changes.
As of atm, it'd involve a pretty large rewrite to be implemented in a "clean" way into the mod.

This is planned, but probably won't be part of the 1.12 suite of changes.

In the mean time if you really want something like this I believe someone in the discord has managed to do a similar thing by disabling manual leveling up and keeping track of progression through Vanilla Scoreboards. So they may be able to help you figure it out.