Ok, I have a Squier Deryck Whibley Telecaster and I wanna customize it.

What I wanna do is add another pick-up and add a killswitch

This is what the guitar looks like

The main problem is that I wanna put in a neck pick-up but the gtr was made for only that 1 pick-up on it, so there is no hollow spot for a neck pick-up to go, what do you supose I do about this?
Have you taken the pickguard off? I reckon that the body is routed for a neck pickup.
yeah just rout out the body, and you'll have to probably put in a pick up selector, just use a schematic based off of a 72' tele deluxe.

you'll also need pots for the new pickup, and a new pick guard. if you really want the neck pickup.

the kill switch is easy, i put one in my squire tele deluxe no problem. theres a whole thread for that though, try there.
Check to see if it's routed for a neck pickup. If it is then all you need is a pickup selector if you don't mind having a traditional tele style wiring (3 way, 1 vol, 1 tone)