Its nice to revisit this thread although I have to admit I was turned off by UED for UT3 and its non-user-friendly interface. Everything takes longer, so a project of this magnitude should take a few years easily, even with a dedicated team. (Is Epic listening? Bring the real Unreal back! Don't give us another half-assed single player game like Unreal 2.... oh well, I think they make enough money from Gears and UE3 licenses, so they won't care about Unreal SP anyway.)
We could use UE3 to do the mod, however, because many of us like the many graphical features of UE3. I would like to see how UE2.5 held up. In fact it would take much less time to do the same thing in UE2.5, and Unreal 2 didn't exactly look bad. The art direction in UT3 and UT2004 left a lot to be desired however, and I think Unreal 1 had some great art direction for its time.
The objective here should be to recreate the atmosphere of Unreal 1, while side stepping some of the issues of UE2.5.
Weapons wise, I think it wouldn't be a bad idea to recycle some of the effects from UT2004, while creating new high poly meshes. How well with a high poly map or models run on new systems (while UT2004 was really optimized for 2005's machines)? I think pretty well. Your average joe whose machine has an in built graphics card like an Intel X3100 may end up experiencing a pretty good playthrough of the mod. So this is really something that favours most enthusiasts of UT2004 (and Unreal 1). I think we should keep Unreal 1's stock of weapon models by and large, although we could recycle some effects. (Imagine what a high polyon Eightball would look like!)
We could recycle some Skaarj models from Unreal 2, but I like the green, organic looking Skaarj and their white armour clad counterparts better than the heavily armoured Pre-gears of war Skaarj who don't wield the same weapons that the player does.
I think we should provide more background behind some of the enemies. The Brutes for instance - genetically engineered monsters, or the Pupae. Introducing cocoons or hibernation stages of the pupae that, during the story, turn into the Skaarj would be another nice idea, IMO.