I've added DB15 connectors to two MadCatz Wii fightsticks and changed the buttons and joysticks. Other is sporting a Sanwa JLF with a 2lb tension spring, Kowal 1mm oversized actuator and an octagonal gate along with Gamerfinger buttons containing black Cherry MX switches, and other has regular Sanwa OBSF buttons and previously had a Crown stick, but currently equipped with a stock Sanwa JLW in 4-way configuration specifically for Daimakaimura.
As for the "supergun".. It's basically just a pile of cables, PSU, 8-pin mini DIN for A/V output, pots for RGB level adjustment and DB15 connectors for joysticks. I have plans for building a proper supergun into a 1U 19" rack box and I've drawn some preliminary schematics for it, but seeing as my current solutions works just fine and I'm flat broke, this project has not progressed quite yet. Only planned feature enhancements over the current solution are power and reset switches, audio mono/stereo switch with transformer isolation, PSU output voltage display and RGB sync strip (LM1881). I've also done some preliminary investigation about an RGB distribution amplifier (have two A/V outputs), but not yet clear if I want to build my own - possibly one inside the supergun - or use a 3rd party external solution.
My primary source for supergun building related info:
http://hacks.slashdirt.org/hw/supergun/
One thing worth mentioning is the choice of 8p mini DIN connector for A/V. It's cheap, very easy to install cleanly as it's round, and standard connector for Micomsoft Framemeister and NESRGB mod. To hook it up to a SCART CRT, you'll need a custom cable (
http://etim.net.au/shop/shop.php?crn=203&rn=543&action=show_detail), but the benefit is that it comes with a boost converter that generates CVBS and RGB status signals, which are required by the SCART standard. In practice, it means your TV will automatically switch to correct AV channel and show the picture in correct aspect ratio. I've seen many cases where the TV remote is lost or broken, and people are stuck with 16:9 aspect ratio on their RGB modded consoles.