I think it's an excellent idea. With a bit of planning, a track could be put down in a session with some testing and fun bits added in. It would be good advertising with many an onlooker, and more so on a sunny day! Maybe situated in the patch of green with the statue in, between seating and car park, as it's already fenced quite nicely. Mmmmmm, a pump track with some awesome berms.
Alister