Gravel Pit is indeed a good map, and one that we have supported off and on for several years now. I have been very happy every time it comes back. We also tried a 24/7 CTF Well (after the changes made to the map in the Pyro update) server which I was
extremely fond of, but it lived a short life before being replaced by CP Well, then something else entirely. If memory serves, we also had a Granary server before I joined.
I do not recall us ever having a 24/7 Hydro server, however. If there are enough people who love the map and can keep the server full, I am not at all bothered by them having a server for themselves. It is one more area for us to recruit from, and possibly to give people experience with a map they haven't tried very much themselves.
I don't have a large amount of experience with the map, so I won't argue about the gameplay. I despise 2Fort instant respawn, but I don't think we should take down the server. All I am saying is that if it draws players and members in, I support the i4dea.
In the meantime, I'd recommend drumming up enough support to hijack the Valve Maps server and RTV over to Hydro. It's worked for the Turbine crowd in the past.