Yeah, i did the same sort of thing recently with an SLX lever (generously donated by Vorlich, of this parish, to whom I still owe a bottle of wine). I dodn't take photos, but it works really well. Ergonomics are spot on!
Basically, you (carefully) take the shifter to bits, and when the springs all come pinging out you're done cos you don't want them anyway. vtje - I think the other side of the lever might have some allen screws that will be the next stage, there might be a cap to prise off the central one, at the other end of where that flat spring is held.
I took out the downshift lever, to leave just the cable pull mechanism and return springs (which are a pig to get back in). The central bolt through the mechanism seemed to have a tapered thread to hold it all together - a bit of aggro and a vice solved that, but I threadlocked it when it went back together.
In short, if you've got or can get an old shifter, there's nothing to lose by trying!