I used to play on a server where they had an online map on their forum. The map was very useful when looking for an area to build, and would be an incredible tool for those looking to place a town. I can't remember the name of the plugin, but if we could get a map (doesn't have to be live showing people, just blocks) it would be great for the community. (If it helps this get accepted, maybe only offer it to people who purchase the forum upgrade to incentivize them to get it.)
Assuming you mean something like Dynmap: I believe ECC used to have one which was then removed because of lag. If I recall correctly, this was back in the days before Rising - which means there would be even more server load now.
-1 Good concept, bad plug in Maybe if there is just an official town listing fourm where town names can be listed with the possibility of cords and/or original owner ign (There may be one of these officially, I just don't know where it is and I'm to lazy to search)
It can easily be done with Overviewer. The map doesn't need to be dynamic or instant, just updating it once a day is plenty. And speaking from experience it causes zero lag.