are you going to gut the sticks (just use the top panel/stick/buttons) or just have a place for them on the control area (so theyre removable)? reason im asking is cause if you were planning to gut them, an alternative would be to get an actual arcade control panel, letting you keep the hori sticks intact.
i bought a sega one (ordered astro city, they sent blast city) from excellent, cost $138(usd). not sure if they do business with switzerland (theyre in hong kong) but its worth a shot if you want to try going that route. it was a 2 player layout, all sticks, buttons, and wiring all already set, and came with the screws to put it in place. course its only 6 buttons/player instead of 8 if thats a concern. you can sorta get away with a 4 button layout (neogeo) if you use the bottom left button as the first, and the top row for the other 3 buttons, cause the way the bottom row is offset to the left a little:
anyways just an idea. this lets you save the horis for anything else, or just sell them for some extra money. good luck on the project.