On a per run (not per floor) basis:
First revive = 45 seconds of waiting
Second revive = 90 seconds
Third revive (and all after) = three minutes
Entire party is down? = Back to Haven in thirty seconds unless someone sparks or has their timer ready.
No more emergency revive. That's good but now you have this as a safety net.
Players must click on people to revive them.
Sparks of life would stay. Energy revives would stay. You get out? You come back as long as a team member is alive. This mimics the way the old revives worked because now it's based on party rather than individual, but keeps the new and improved not-dying-everywhere mechanics. Sparks of life would still be very needed for difficult areas that players aren't prepared for, and would still be nice to have for skipping the timer.
I'm trying to think of a scenario where this wouldn't be helpful but it really works pretty great. 3 minutes is a long time for an action game, so hard areas would still require sparking. Team wipes should also negate any timer currently active so that it requires a spark to avoid returning to haven, and reset them upon someone sparking (from 3 minutes down to 15 seconds, you're out for another 3 minutes from the team wipe. Better to just spark in this case).
My only question would be how much health is revived by this method. Sparks give full health, but would a timed revive revive full red hearts like an ER? Or perhaps they would only restore half your HP. Maybe even just revive you with 3 pips of health like a clockworks elevator, making sparks mandatory for difficult content if you're taking a lot of hits.
Have to say I really do like this idea. It's a look at revive mechanics that I haven't even considered before.