Everything will cost something to maintain, hard to get around that.

As far as on time performance, airlines allowing passengers to blatantly exceed carry-on baggage limits and rules certainly does not help that. And it's not so good for safety either. And this is ignoring the irritation to other passengers who follow the rules. As far as how unsafe extra baggage in the passenger compartment is, I don't know. Common sense would tell you the less the better though.

Plus, the airlines have already found a way around on-time performance. Back many years ago, the flight from Austin to Denver (one I've taken many many times) used to take a tad over 1-1/2 hours, and they advertised the flight time as 1:45. Then they started advertising it as 2:00. Now, I think they're up to advertising it as 2:15. I'm pretty sure the two cities did not move farther apart. Pretty much these days, any continental US flight could probably divert to Tasmania during an emergency, and still manage to make their scheduled destination on time. And that's with in-air refueling and a stopover in Hawaii for mandatory pilot rest.