First of all, you didn't make it clear that you meant a "modarchive" station, you just said a "community radio", hence the notion that there already exists such - not that there is no interest in your idea. But I personally feel there is little need for yet another streaming station.
Besides my personal feelings, and those technical issues outlined by Saga - who's going to pay for this? Servers don't come for free. I struggle to get by as it is on the donations to keep this site on-line, and that's with a very cheap dedicated server hosting plan as it is. To do a radio would require another server, the current one is maxxed out running this website alone!
The immense amount of work (as Saga stated) just makes this a detraction from the purpose of this website, and is just, well, unfeasible in an "official" capacity.
If a community member wants to set up an "unofficial" station, then there is nothing stopping them from doing so if they really want to put the effort in (and money).
By the way, you'll find that Nectarine (scenemusic.eu) has essentially pulled most of it's music library from modarchive, and setting up a competing station against Nectarine - which has already faced it's own set of setbacks recently - would be like us stabbing them in the face with a broken hard drive.
We're scene family after all.
Another stream you might be interested in
http://www.bitfellas.org/e107_plugins/radio/radio.php