Okay, I'll tackle a bunch of stuff here:

First, my suggestions. The one thing I'd really like to see in this RPG is a cool and complex character development system. Along with a fun combat engine, the heart of a good RPG is great character development. The one thing I'd hate to see is a very simple "Get x number of Exp. to advance to a new level, where each statistic will slightly increase." It's certainly not *bad* but it's none too interesting after a while.

There are a couple ways I know to have a cooler system. The easiest one (and it was mentioned previously) is a class set-up. You can pick classes for your characters, and this effects how stats increase upon each level up. If you want to make classes even neater, add in some way to change them. Either just being able to change them at will (but maybe having pre-requisites, i.e. if you want to be a Ninja, you have to have been previously a Fighter and a Theif) or having to get to a certain level or find a certain item to change classes.

Another neat thing that goes a long way to make building characters fun is to have unique skills. This generally goes along with classes and allows you to have some control over how your characters develop. An easy example of this idea is the concept of spells - they're skills that (usually) only Mages can learn. If each class has a couple of unique skills that can be learned only by someone in that class, it really allows characters to have a sort of individuality.

Lastly, I'll give my take on multi-player. I think it'd be very cool (even though I tend to dislike Java because it takes forever to load on my old computer -- I really do plan to build a new one ASAP). As for things like picking on newbies, I'd have to go with the idea of a special room that was just for battling other parties. I've never gotten into MUDs because I hate playing in the presence of Level 999 players when I'm still celebrating getting my guys up to level 4. But if you specificially wanted to do some player combat, it would be great fun.

But I'd think it'd be best if there was a consequence for losing in addition to a prize for winning. How about a way to wager experience points or gold or something? And how about some sort of Ladder System with points you get for winning battles, so that we know who's the best? Heh, that'd be neat...

Anyway, I don't know how doable most of these suggestions without knowing much about your game. But I just had to get into this thread...