Honestly I don't agree with those suggestions at all. I mean sure they would make her better, but they aren't reasonable asks. Rest killing at 30~40 would be insane in a game where 2 stocks are standard. Plus, Rest already does have 8 invincibility frames. I have no idea what you're talking about when saying a Rest is mid-low reward considering its kill potential compared to other moves is high, and regardless it will consistently deal 25+ damage. Just... don't use it when it wouldn't give you the kill but put you in a bad situation? The only thing to be fixed in this regard is the capacity to get a blast KO and be punished on respawn.
As far as uptilt goes, a weaker start might be nice for combos, but its KB scaling is also so huge that it turns into a viable kill move. I don't think I would want it to be weakened for early combos and lose the KO potential.