I'd like to see this added, it can be very helpful to both server owner and player. A lot of times players like to be there on opening day, and even before that. Sometimes people like to get a feel for the community before joining, like posting on the forums and discussing suggestions or requests before opening day. People are also more apt to partying for that 'Novice Rush' if they know a few people from the forums. Many people out there like 'fresh starts' when it comes to servers, and this would definitely be a big help.
Server owners like to get their name out there in advance, so they can perhaps catch players before opening day. Believe me, it's a lot more satisfying when you have several people on when you open versus not having anyone at all. It's nice to see what sort of community you might get, and if your server doesn't seem to be attracting people then you know you're doing something wrong and can work to fix it. I see it being good for the server health because suggestions are easier to impliment when the server is untouched (at least from my experience).
I realize RMS does allow a 'grace period' of a week or so before opening, and I do think a month is too much. Three weeks would be perfect, if possible. It'd be nice to see a sub-board or anything of that matter for upcoming servers. Of course there would have to be requirements for this, just like the other server advertisment sections. If this was added, and you didn't want to make a server section for each type (Low Rate, Mid Rate, etc.) then have it be a requirement to post your rates in the title of your advertisement. Those who can't follow the rules, well they just get theirs taken down. I'm also not sure if it's possible, but maybe the advertisements could be deleted after so many days of being posted?
I don't know, that's just my two cents. I really like the idea, and would like to see it added for future reference.