I have to admit that I love the instant-replay rules in college football, because particularly inept officials aren't allowed as much of an opportunity to influence the game because the coaches have run out of challenges. And because the booth technically reviews every play, nothing goes unnoticed -- unless it is not a reviewable play.
That means that the number of plays that are reviewable should be as high as possible: If what happened on the play can be determined with some degree of objectivity, it should be subject to another look-see. That should also apply to some penalties -- the ones that are largely objective should be reviewable.
What are some penalties that I would include in the list?
Face mask: This one is, to me, pretty easy. You can clearly see on review if the player in question is grabbing the face mask or not. The review would be limited to that question -- did the player's hand make contact with the face mask? -- and not whether it was long enough to be penalized. It's a 15-yard penalty, we ought to be able to make sure.
Roughing the kicker: This would prevent players getting flagged because the kicker pulls off a particularly convincing swan dive. The only question would be whether the player actually made contact with the kicker. The call would stand unless the replay showed no contact.
Block in the back: How many times have you seen a block in the back called, only to see a review show that it was a block in the side or something else. This is one of the iffiest ones on my list, but keep in mind the standard for overturning a play: Indisputable video evidence. If it's clearly not a block in the back, the penalty is waved off. Otherwise, the penalty stands.
Intentional grounding: We have telestrators now; how hard is it to draw a line on each side of the tackle box and figure out if the quarterback crossed it or not? I'm not sure which side would benefit more from this, but as long as video can show what happened, there's no reason to get it wrong.
Encroachment / off-sides / false starts: Again, only if it's a clear case of the other guy flinching first. My guess is that the booth isn't going to call down on this one very often and most coaches aren't going to use their challenge on a five-yard penalty. But if it's a critical call at a key juncture of the game, such as fourth-and-one in the opponent's territory on a significant drive, it might be nice to have the option.
It's not going to happen anytime soon, but it should be -- um, reviewed -- in the future. College football already has the best replay system in the game, but that's no reason not to make it a little better.