It's all in the layouts, make a conf file that calls a lua script that draws a guage or whatever in cario, there's plenty of examples on the net.
Drawing in cairo is a learnable skill but yeah it is just like coding so we can all claim to be busy or interested in other things and not do it. I have no background in drawing and i hate having to worry about memory leaks in lua, so good luck convincing me to do it. What I don't understand is why nobody with an n900 has tried yet (and showed us the results). Angry birds graphics are done with cairo btw, so it isn't some weird drawing method, and lua is pretty much like c++. Did you ever look at some of the conky layouts on ubuntoforums or other blogs?
Apperently n900 owners have no talent, knowledge or time? Anyways, yeah, no rewriting conky, it's a lot easier to just make a fancy layout. Performance is a problem though, if you try to do too much. If you don't want conky to use 3 times more cpu i would leave it alone...