I've taken apart my Clevo laptop to do maintenance and repairs before.
There's almost no wires going in/out of the motherboard and you're pretty much stuck with the shape and location of all your I/O and the DC connectors. The heatsinks and fans are usually positioned and/or made specifically for the laptop model, so there's no salvaging that. The motherboard also isn't built to accept anything except laptop components, so any aftermarket coolers can be tossed away and you'd have to either reuse the same fans/heatsinks from the laptop or create a new one yourself.
The graphics card could be salvaged, but it'll probably MXM form factor. There's almost no motherboards on the market that would be able to accept MXM cards. The only ones would be the proprietary stuff from MSI or Zotac or Gigabyte mini-PC attempts like the Zbox or BRIX.
If you want to use the whole motherboard, then depending on which laptop you obtain, you might be able to put together something like an Intel NUC, but with a dedicated graphics card inside. It seems silly though to do this when gaming laptops are already pretty small and portable. Clevo had an 11" laptop in 2012 that could run Battlefield 3 on an external monitor at high-ultra settings with temps at around 60C-70C for both the CPU and GPU. That was four years ago, and I haven't seen how much they've improved since.
