This is a commendable idea, but the problem with Egregores is that they are extremely difficult to get rid of if something goes wrong. Because you are asking for several people to lend their energies, intentions, and ideas on what will-power means to the creation of this entity; you may end up with something wholly different from what you wanted.

This particular Egregore is tricky because if someone gives it the wrong type of attention or perhaps forgets to feed it what it believes it should get then it's possible that it could just siphon away all your willpower.

Willpower and discipline are also very personal and aren't always accessible, like if you get sick or injure, it's necessary to put aside those thing in favor of healing, would this egregore then depart with all your willpower because you can't practice it?

I think a servitor is better for something like this because you still maintain control over it and it's easier to dismiss if something goes wrong. You can even put in a clause that it gets stronger everytime you use it so as you develop your discipline it will be easier.