Consider this: even a monk has two "dump" stats, and they're constantly crushed on these boards because of their need for multiple stats

But.... that's not relevant. At all.

See, while it's true that caring about any more than 2 primary and one tetritary stat leads to major problems (MAD) that does NOT mean that removing the -2 penalty is good. Those two things are only tangentially related.

Even for a monk, the ability to not have a -2 on your race is not awesome. Cause a -2 int as a monk helps you none anyhow. You it's not great to remove that -2. The minor ability might as well say "+2 to a dump stat".

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).
No it isn't. You'd have to know when your encounters are going to start (Because mintues/level means that it will usually ware off before you reach an encounter if you're just wandering around hoping an encoutner starts) OR use the first round of combat being buffed by your caster for that to be true.

PCs don't usually know when well over half their encounters will occur , at least in my experience. The 2nd is a signifcant oppurtunity cost, espically as levels go up. It's not a spell lost, it's a ROUND for one of your parties best party members. Imagine this ability was instead, "Give your arcane caster an additional action each combat", would that not be an overpowered ability?