I think it would be a great idea to have a beatmap request forum, with links to songs that beatmap maker's can look at and think "hmm...that's not a bad idea" or "nope."
There was a thread for requests before but it's just really ignored as most mappers just map what they like so bringing this back (specially it's a forum) will be useless.
Sadly, we're probably not going to see a forum like this anytime soon. This post basically summarizes as to why, and you can see for yourself as to why such a system doesn't work in the long term.