i think that the netplugin interface would not restrict it to 2 players. So it is possible technically. but in practice, it'd strictly be a LAN thing. if you're thinking the internet, you'll need a very very VERY good connection, at least for the server.
i wonder how many games are compatible with that. the only one i have is Descent Maximum (of which single player works pretty well in 1.4.0 btw). But I doubt the netplugin interface supports that right now. It'd need another interface.
if i'm not mistaken, FPSE has that capability, you just need someone to code a plugin for that (hint, hint)
As far as I was aware the cyberpad "emulates" a controller in the emu (hence the name). Thus if the game supports 4 players on a real psx AND the emulator suppored 4 gamepads then you could use this setup.
However epsxe doesn't support 4 pads and if its the same iss that I have the game doesn't support 4 pads. Either way your out of luck I'm afraid.
What Betamax say is true.
CyberPad can only "emulate" the pad's which the emu support.
Currently ePSXe support "only" 2 pads, that means CyberPad can also only support 2 pads.
If ePSXe should support somewhen 4 pads, we need to rewrite the complete plugin to make 4 pad's workable with it too.
But I think to have 4-player support in CyberPad isn't that important than a better gameplay, yet