True, but most of the other shapechange effects do have a duration limitation. Such as the druid's change of 1/hr per level. Which really is a very long time... Anyways, there is still a limiting time factor.

Now would you start off as humaniod? Or would you be your own special race called eidolon gone wild? (Sorry couldn't resist)

What type of BAB would you go with? Saves? Would you change those based on the type of form that is taken? Do you always have to be in the Eidolon form? Or does it need to be its own race?

Truthfully I think it would be a cool class to play. I am going to be playing a summoner in my next game that I play so it would be kinda of interesting to skip over some of the spell casting and go straight to the fun of changing things around all the time.