@OldNick/@RealFBNick, there are actually quite a lot of discussions here about cooking two different done-ness of steak for the same meal here. Just a matter of digging to find them. Here’s one I found for you: Cook a medium rare & a medium steak in same batch?
The basic idea is to cook the higher temp steak first but only long enough to reach temperature equilibrium. That’s around 30 mins per half inch of thickness. The water bath is the dropped rapidly to the lower temperature and the rare steaks added to the bath. The higher temp are fine to remain for the duration. The will not turn to mush as that requires very long times at low temperatures.
This method is the most efficient way of achieving your aim.