The RS build is still being worked on by me btw, it is just no longer open for people to see athough you can go to our website MineFutures.com to see some semi regular updates and look at the New server "Outremer"
I didn't read through all other pages so I don't know if anyone else has suggested it, but if you plan on making this an RPG server, or at least someone else will, then it would be awesome to have member only areas actually be members only. Paying members will get the best parts of the server. Also, outside of the Runescape world you should have more world, that way people won't ruin the regular Runescape world, and can build outside of the regular Runescape world.
Other ideas would be something like having some custom plugins for your server, like a home plugin. If you decide you can buy a home from an npc realtor, go through one of those portals to your house(I haven't really played Runescape in years), then it would put you on an empty space that you can build on, and you would only be able to use certain building materials in the first area, then you can buy with economy money more rooms like Runescape. And invite people to your home and everything.... But that's just one plugin idea.
if you want i can do some of the member world stuff and i bet the dungeons have to be hard and dont forget the skeletons and stuff in the dungeons im sure you can hack to make it give like the moss giants and stuff and well minecrtaft already has wolfs so no need for them to be put in