It looks like G-Engine will shape up into a very impressive web app.

I just have some ideas based on playing WoW and Champions Online.

1) Skill trees. Where you can choose and upgrade skills set out in a tree style, it would really add to the game.

2) Combat. Champions lets you add your combat skills to the boxes along the bottom, and you click them in combat to use them. It's very convenient and versatile. Also they show recharge times.

3) Guilds/Teams. Join guilds or hook up with other players in a team.

4) Transparency overlay to darken graphics at nighttime, possibly also to show depth of vision, like in caves or dungeons, or in the dark with a lamp.

5) Compulsory quests and optional quests.

6) Private chat, team and guild chat.

That's all that comes to mind right now ;)