I know pathfinder is not played nearly as much as 3.5 on this site, but I figured I'd send this idea out.
For those who are unfamiliar with this intersting creature, the below will give you all the info you'll need: Eidolon
As it stands, the creature does get a decent amount of options at each level, but lets make it a little more awesome:
1. The abilities could be removed in place of different special abilities. (Still uncertain on this one though) 2. The Eidolon acts as though under the Unfetter spell at all times, which cannot be dispelled or removed except by it's original owner (fluff). 3. Eidolon's gain an additional evolution point at lvl 1 and at levels 3, 6, 9, 12, 15, 18. 4. Eidolon's may use the Transmogrify spell 1/week. But may use this spell every time it level-ups; using it in this manner allows it to change its base form as well. 6. Prerequisites are still needed for certain evolutions but are based on the Eidolon's level, not summoner. (ex: an eidolon must be at least lvl 5 before choosing the Flight evolution. 7. They are given spell-like abilities and may use them an additional number of times per day at certain levels: