My first reaction is to say "Just get a smartstrip" which (if you don't know) is basically a power strip which will shut off power to outlets 2, 3 and 4 when you turn off the power to whatever is plugged into #1 (a simplified explanation)
But after reading this:
Any thoughts to control in an easy way the ON/OFF of especially the Light and Monitor? PC will remain on like I said most of the time, so no bigee there.
Then it looks like you'll need at least 2 switches somewhere. You still don't have to have three wires (or even 2 wires) running out of your cab, but you'll need some way to switch the light/monitor off while leaving the PC running.
So, you could: put a powerstrip inside your cab (as many people do) and then run the power strip plug out of the cab and into your wall. Leave the power strip on all the time and rig up two switches on your cab. One for your PC and one for your monitor/marquee
OR, some people have computers which can be set to turn on when you press the space bar. If that's the case, you can just rig up a single power switch which cuts or supplies power from the power-strip to your light an monitor. Again, leave the power strip powered up all the time. You hit that switch and your light and monitor should just turn on (or off). THEN, you press your spacebar (or whatever button you have associated with starting up the PC) and you're good to go. Using Mamewah (or other front ends) you can shut down your computer from there.... and then start it up via the spacebar again when you want.
OR you could just put in a bunch of individual switches. I wouldn't go for the gangbox & lightswitch option though because, IMHO, it looks really really cheezy to have a household lightswitch on your cab. If you DO go that route, then at least use some kind of low profile rocker switch like the one below.
It's easy to 'hide' toggle switches on a full sized cab. Just put them on top. Recess them into the wood and nobody will see them. It really all depends on your priorities, I guess. Would you rather have a one switch solution or do you really want to be able to switch a bunch of things on and off independently of each other?