Have you thought about a simple 2 joysticks, each with 6 buttons (Street Fighter layout).
and for the joysticks, you can use Sanwa JLWs or Seimitsu LS-32s which are switchable from 4-way to 8-way (true restrictor)
or you can use Ultimarc Magsticks (modified Sanwas?) which can be switched by pulling and rotating stick.
Or of course the Ultimarc U360 which can be mapped for 4 or 8 way.
just some ideas. otherwise, search the forums here, there are many examples of every type of setup; Simple classic setups, Fighters, swappable, modular and of course Frankenpanel
good luck