Actually I managed to open it right after posting the OP just by firmly pulling the bottom plate with a screwdriver in one of the numerous holes drilled in this plate. Here is what the bottom looks like:
I removed all the guts and there is quite a lot of space in there, enough to hold a PCB, two jacks, some pots and a switch. Perfect to host the Musikding Tremolo kit I am lusting after for a while now inside. I don't know if I'll manage to achieve it, but allowing the tremolo speed to be controled by foot with this pedal should be very cool. I tried to put two random pots in the place where the plug was, it is a perfect match. Once the nuts are tightened up it is very snug. the remaining jack plug in the middle should be easily be cut with a dremel and replaced with a 3mm LED.
I am still a bit worried by all these useless holes drilled here and there on the enclosure, but I have found that a French product called Sintofer (a kind of resin used by auto body repairers) would do the trick, by applying a thin sheet of aluminium under the holes I want to cover and filling them with the Sintofer.
At least the two square holes under the pots are very well placed to let the rack and pinion pass through the enclosure. Banzai Music sells all the wah stuffs including the rack and pinion and wah pots, so I'll order with them.
I am now working on the spindle of the foot plate. I'll use a threaded rod covered by a tubular rod, mounted on a triangle-shaped caster frame and fastened together with two nylon locking nuts. The system needs to be worked a bit as it stands pretty high on the pedal, but it should do the trick. The picture just displays one of the two spindle stands, as I screwed up the other one when I removed the caster from it.
To think about!
