I'm just willing to throw my few sents regarding the developement. I'v been currently playing around with my own engine, and I'd like to see few ideas thrown to mana world.
First, take a look at some concept-pictures:
http://www.tamk.fi/~c4jlepol/concept-shot1.gif
http://www.tamk.fi/~c4jlepol/concept-shot2.gif
http://www.tamk.fi/~c4jlepol/concept-shot3.gif
http://www.tamk.fi/~c4jlepol/concept-shot4.gif
Currently the engine is only capable of rendering moving ball's (actors & objects) and I'm slowly getting to work with polygon-based landscaping...
So, one recommendation I'd like to see would be adding facial pictures of npc's and pc's. Basically game would include face-gallery, and by clicking other pc or npc it would open 'target window', which would show some basic impressions about the character (as seen on concept-shot1). This would occur in situations such as when having conversation with other character... somehow it add's more depth to the game.
Well. Being able to hide toolbards and open 'em quickly would be nice. Someone already suggested this in another post. Also being able to chat simply by starting to type in keyboard would be great. I prefer not to predefine action-keys, and some games leave keyboard alone just for chatting.
Something to concider: I have made a documentation of new MMORPG theme based on ownership. This system basically works so that every object / tile / scenery has relationship with certain owner (such as group or individual). This would mean that anyone can own anything, and this add's possibility to further impliment new features, such as adding bonus feats when accessing certain tiles. Ownership is something which all MMORPGS are still missing, yet it is one of the easiest implementations to make and would give endless possibilities to make deep infastructure for the game... I'm not going to further details here, but If you are interested, I have lecturing documentation ready. It's something I researched for my schoolstudy and which I'm going to implement on my own engine.
If there is anything you need help with, I could lend a hand.
[edit] Oh, and fix the targeting of npc's. It's annoying when character just moves behind npc when you'r trying to have a conversation with it

[edit2] btw, how big tiles can the engine & mapeditor handle? I was just wondering if sizes such as 512x512 are supported, or are tiles using some fixed-size (64x64)?