Would you pay for chapters that include new features but not content?

I would. In fact I'd pay $30 for the following and only the following:

1. The ability to reenter an instance after a crash, hang, or disconnect and pick-up where you left off, so you don't have your party doesn't get screwed and you don't have to repeat the same mission over and over through no fault or your own or that of your party's.
2. Ten times more vault space then we get now.
3. Twice as many character slots as we get now.

If you would pay for chapters that had no content, but only new features, what new features would you pay $30 for?

No, that's a patch.

Ding ding, we got a winner.