What's irrelevant is what the Lib Dems either proposed to do or propose to do. They are not in power and are not taking the decisions at the minute. It's like saying there's no point in debating the coalitions economic policies because Labour would be doing something different.
The problem with this whole shooting match (and I've told Henri this) is that there are too many issues all being rolled into one and this is diluting the argument.
Issue 1. Can QPSC be legitimately saved and refurbished. Answer almost certainly not, the pool end is effectively 40-50 years old and the leisure end 30 years. It was a poor design concept in the 60's probably worse in the 80's. The whole thing was done on the cheap and that decision is now proving to be the centre's downfall.
Issue 2 Should it's replacement be built on the annexe. Answer almost certainly not, the annexe should be re-furbed and used properly. It could be used for athletics events, concerts, fetes and galas as well as providing a much better finishing point for things like the Race for Life, Hospice Drag Race, the new proposed marathon etc etc.
Issue 3 Should a new leisure centre wherever it is built be part funded by another body effectively rendering a public building out of public use for large proportions of the time. Answer again probably not though of course you then have the argument can the council afford to go it alone?