IDE Feature Set

I'm currently traveling down the road others have gone and trying to create an UnrealScript IDE myself as well. nFringe and WOTgreal and some of the newer attempts are all usable and nice, but none of them are as lightweight as I want and are either missing key features, aren't extendable to include features I want, or are outdated. Hopefully I should have a prototype by the end of the week, but if you have any suggestions for what you would like to see in an UnrealScript IDE please comment away your suggestions.