It is pitifully simple to get large size for a good length in core only (Enlarge Person is mins/level, grab your arcane caster a pearl of power or two at 1000 GP each and you can easily have it all day). Just make them monsterous humanoid/giant or such so they can't stack with enlarge person (if that is still not enough, make it scale over a few hit dice like raptorian flight).
As for the topic it's self, can you trade for two options on a lesser menu?
Good points/plan. I was wondering how to deal with the problem of Small creatures never having Darkvision.