I highly approve of this. I always loved his best -- just edging out Viper and Backlash. As to approach, what's your skill set? Over in the Star Wars section, in Fierfek's Star Wars pepakura thread, should be a link to a pep Royal Guard helmet. That'd make a good starting base if you're comfortable modding something like that after stiffening. Work-cost versus material-cost. Yeah, you're dumping valuable time into it, but IMO that beats butchering a replica helmet you've plunked down upwards of a couple hundred for (what I tend to see them for out there). I've used pep patterns before as templates for sintra, and I've seen them used for cutting thin (2-3mm) craft foam in similar fashion.
If you're set up for mold-making and casting, you could take the pep build, fill it in, and then add on and cut away as needed to make the initial sculpt and go from there.
Hard to know what direction to point you without knowing what you have on hand and what you're good at, that you could get it done in that timeframe. I mean, you could always model and 3D-print it. *shrug*
