Anyway, I'm planning on using a Seimitsu LS-32 as the stick -- but I'm not sure what buttons to select. They have to be microswitched yet not have too high a resistance
I think the stick is excellent - I´ve had a Sanwa setup for almost a year now, but when I recently had the occasion to play for one day on an Astro City with a Seimitsu stick, it was not the Astro City that impressed me, it was the Seimitsu stick. With buttons, however, Sanwa is better.
You say you want microswitched buttons - have you ever played on an arcade cab with those? All of them have a much higher resistance than those used in Japan. They are probably very much vandalism-proof, but when you want to play comfortably, look elsewhere. I mean, it´s not like Sanwa buttons would break easily, really. During this one year I´ve had my setup, I haven´t noticed any performance loss with the buttons, and that´s very different from my experiences with several arcadesticks for consoles.
I know one type of microswitched button with little resistance, though - the buttons in the 2nd revision of the old Commodore 64 Competition Pro joystick were easy-going, but worked with a microswitch. They were concave, however, so for an arcadestick with several buttons where you might want to switch between buttons quickly on occasion, they´d probably perform sub-par.