I am absolutely sure there would be no contraversy about building on the Rec. I am sure the Civic Society would get right behind it

One interesting thing to consider is that the council hold the freehold to the delivery office. With strealing some of the car park, a four or five lane 25m pool would be doable I reckon. Second floor being a gym, studios and stuff. You could even make it three stories and have parking underneath. You can fit a lot into a compact space if you try.
But as ever with these things, it's a matter of money. Tameside are spending something like £14m on their new complex in Denton. That's having an eight lane 25m pool, small pool, gym, bowling alley, and soft play. But still, a new pool and gym for Marple will cost a few bob.