How about adding a level 2 on regeneration?

The level 2 regeneration won't be as powerful as the other boosts, it will work just as before. BUT, this time it will work on passive mobs and villagers that are hurt.

Im not sure this is a good idea or something but i find it kind of sad that you can get a wilder-item (that normally get you really excited!) and that it won't do anything special, if not regen lvl 2 then maybe a wider range once the pyramid is maxed out on level 4?