It may not be doable and even if it is, it's probably not worth doing.
Why it may not be doable: Few new Laptops have an Express Card to rig an Adaptor and hackery with the Mini Pcie Slot that the Wifi Card uses is whitelisted thanks to the infinite wisdom of the FCC.
Why it may not be worth doing: Older laptops that don't have the Whitelist or are Core/Libre Boot compatible have older CPUs that bottleneck the GPU, The GPU is bottlenecked by PCIe x1 anyway, even if you still want to do it and have a non-free Bios, you'll have to go through the trouble of ripping your Bios and then looking for a whitelist flag in that binary blob and turn it off and then flash it. You're also making your system less portable though it would be nice for laptops that have M.2 where you could rig that into a GPU Dock for gaming at home. (Preferably games with free engines :D)
