Ryanair already does a lot of this. They base fewer aircraft overnight at STN than they have done in the past but far more aircraft based overseas come in as the first wave goes out. Look at the STN arrivals/departure boards for tomorrow morning and you'll see how many come in first thing on turnarounds.
There is still a fair bit of unused remote parking and if you've been through STN lately you may have noticed some new gate signage for Gate numbers 90 - 93 which are in a separate area and used specifically for bussing passengers out to these remote stands.