> Ordered instead of ProviderPriorityAware

I agree about using a more generic name. Which package should it be in, then? There are so many to choose from. :)

> it should return int instead of enum

I considered it, but thought it would give a weird combination of false sense of security because of the exactness and paranoïa about getting exactly the right number to fit between two other processors, for example. Which would be bad because it would be relying on another processor's internals.

I feel like a less granular choice warns processor authors and users that they need to be careful and also makes the choice of priority easier.

If you really prefer a number, how about using a byte?