I think the solution could be having a server browser filter servers by download size. If people don't want any downloads then they can easily select max download size at 0MB. I'm not a fan of having a total download limit, as it might prevent servers from utilising fully custom created maps, unless the cap is high enough not to matter. As for vetting servers, I don't think anyone wants to do that, but what could be done is "Open.mp endorsed servers" which have their own tab in the server browser and have been known to be high(er) quality and not using any ripped assets or such.

I do not believe public object pool would be such a great idea, especially for a server that's being developed, especially if it is a part from an entirely custom terrain. Whoever would be vetting these would be spammed with obscene amounts of requests, especially if server's in development. And how you actually develop the custom terrain without having the object vetted first? (Sounds like a bottleneck to me)