I think the answer has to be (in news that will please Sarah) "I probably couldn't" - I'm not sure I've really got the practical knowhow (I wouldn't know the first thing about working in fibreglass, which seems to be pretty much a requirement for at least some aspects of a Dalek), and I'm more realistically looking into the notion of creating virtual models of props with computer programmes such as POVRay. (And who knows, if I can get good enough - a BIG if - helping out in recon projects such as those done by Who3D...)
(And can I just mention - Redders Daleks page has some seriously impressive Dalek pics...)
(Although, in news that won't please Sarah, "never say never...")
In my search online for plans that could be used for such virtual modelling work, I found this guy who's built a whole TARDIS console and console room. And a Dalek. To say that I'm seriously impressed would be a massive understatement...