Which isn't all that new. It happened with relative frequency pre-1980s when the closer role and more defined bullpen roles became the norm.
Right. Like I said, the rule that RPs go no more than an inning is a modern creation. Now, there are some good reasons for it, which is why it became a rule in the first place, but like most things, over time you find a better balance in the middle. You can get greater effectiveness out of a lot of pitchers in just an inning where they can let it rip. But you can also get better effectiveness out of others by letting them pitch a bit more.
There's always a trade off, though. By throwing more in any one game, you won't be able to use those guys as often. So it's probably something that would have to be better planned ahead of time. Instead of just going into a game with everyone available and just taking guys off the list if they've pitched too much recently, it would have to be something where you pinpoint games for certain guys based on the starting pitcher, opponent, etc. And then you just don't use them if the SP is killing it or if the game is not competitive.