Sounds to me like you don't like ANYTHING with that laptop.
Hmm... custom built laptop.... If that thing EVER sees the daylight, I bet it would be the ugliest laptop in town. Putting laptop together out of different parts is next to impossible without a ton of loctite.
I can imagine changing HD or DVD drive. Or even CPU on laptop, but mobo? With laptops, mobo is the core. It comes with everything from graphics to shape and position of screws and holders. So you can't just swap them around. It is simpler and less stressing to ditch what you have and get something else. Difference of the shapes of things, design and all that makes it is practically impossible to swap DVD drives between, say, Toshiba and HP because they just don't fit. Or "almost" fit. Not to mention display. I'm not sure how "standard" is the connection between display and graphic card, but I wouldn't be too surprised if dell's display won't fit on Sony.
And if you DO manage to patch something together:
1 - would it be capable of carrying around without causing occasional fire or exposion?
2 - what would it look like (read: how embarrassing would it be for you to bee seen in a vicinity of one? I'm sure it would have a winning personality...)
The moral of the story:
If you feel creative, build a desktop.