First of all, I have to say I immensely enjoy this The-Ultimate-Geek -Toy.
I love 3D modelling, graphics, making music and coding in first life too. Second life will probably give me an audience

Anyway, to the point.
I found a few features I'd like to see some day:
Scripting:
llGetLandFlagsAt
- This would give you a binary flag mask in some form telling if the editing, creating and so on are allowed somewhere. If it's for sale, and so on.
(easy?)
Interrupts. It may be just because I'm new to the idea of LSL, but I'd like to have some immediate control over some script which is running. Ie. you could give some event "interrupt" flag and it would jump out of whatever context it was doing at the time, execute the event and and return to the previous context. This would ofcourse complicate the stack and require hefty rewriting so I'm not holding my breath


(Hard)
Modelling:
Boolean operations on primitives:
Examples:
- Intersect two primitives and execute substract A from B. Result would be B with shape of A cut out of it.
- Intersect two primitives and execute "intersection" on A and B. Result would be only the intersecting part of the primitives.
No real modification or collapse to new primitive, but this would be done on the fly so only extra info in object stream would be the boolen operation flags and on which objects to do it on.
(Hard)
Mirroring:
Something to tools menu to flip an object around over one ore more axis' (sp?) of itself.
(easy)
Parameter copy:
Select object(s), tell how many to copy and give values per step to how to. transform, translate and rotate
example: You want to have a formation of boxes, spiraling from in to out, each box tilted a bit more than the previous and being a bit larger than the previous. With this you could make the formation with one command once you have calculated the values you need.
It would also be neat to be able to select if you want to use global coordinates, original prims local goordinates or previous copys local coordinates to calculate the next parameters.
(Hard)
That's all I have thought for now. Actually there's a lot more, but I try to keep the ideas atleast theoretically possible in the world.
EDIT: Changed the title afterwards as I noticed I rambled more than I thought I would
