This is one of my more radical suggestions, but I believe the end would be one of the biggest and greatest additions that could be made for the server, so I balanced similarly to the nether was, I know it would be too broken if we used vanilla mechanics so dragon heads and obsidian wouldn't be mineable and item frames won't be generated to balance it a little, emerald rates in chests could also be lowered or taken out completely. To access the end a warp could be made with a portal everyone can use, there's no use in having a personal portal anyway since they share a spawn point, this dimension would also be reset every month like the nether. The dragon would also have to be disabled, but maybe it would be better to /kill it every reset, so there are portals to the outside part of the end, but maybe that can be solved in other way like spawning the portals with commands and just keeping the dragon disabled. You also cannot place end crystals, signs and other stuff like in the nether. I know it's a lot of limitations, but this would give us a new dimension to explore, more ways to get items you already get in fortresses like diamonds and a great place to get shulkers and end stone!