Summary
It would be nice to get an expanded, or all encompassing Experience mechanic. One that does both levels AND points. And has the ability to use negative values (or similar) so that exp points and levels can be both given and taken away.
In current, there are only these two mechanics to give and take away experience levels. but they do not do points. https://git.lumine.io/mythiccraft/MythicMobs/-/wikis/Skills/Mechanics/TakeExperienceLevels https://git.lumine.io/mythiccraft/MythicMobs/-/wikis/Skills/Mechanics/GiveExperienceLevels
Value
In current, to use any experience related stuff, you have to use the command mechanic with the vanilla xp command. Using mechanics opens up the usability of giving and taking xp away from players.
Priority
Meh. Would be a cool feature, but not a priority suggestion.
Implementation
I think you'd really only need 2 attributes. Type (either points or levels) and then amount, which ofc would be any integer, negative or positive. If you did this, you could remove the two other experiencelevel mechanics.
experience{type=POINTS;amount=-10} @self ~onUse