If that mean having an external radiator on you desk to connect the laptop to (like that specimen you linked), I'm not sure I see the point. The internal heatpipe /air based cooling system still need to be able to do the job when that external WC system isn't connected, so this just add a lot of complexity.
Even if the point is to be able to run at higher power limit when not in "mobility mode", I have some doubts about how much extra cooling capacity such an hybrid system can have. The WC loop heat exchanger can't be in direct contact with the chips, but only somewhere in contact with the heatpipe based cooling solution, so efficiency is likely quite low. The main performance gains of WC comes from the fact that it can put a large temperature difference very close to the chip, that advantage is entirely lost there.
This being said, this can be a thing to overcome the usual noise of "gaming" laptops, by deporting a decent fraction of the generated heat to a more silent cooling system. But personally, I would prefer to see more development on an actually viable external GPU solution, that seem a more sensible approach to the "single machine for mobility and gaming" problem to me.
