That was exactly my thinking. Here's my post to reddit asking the same question.
"Asus G75vx eGPU Compatibility
Hey all, first post here on Reddit. So I have an Asus g75vx with a 670mx integrated gpu (laptop). Currently, I am running a modded bios for overclocking the base and memory clock speeds. My current base clock hovers around 950 mHz, whereas the memory is around 2400 mHz (using nvidia inspector). I have removed the bottom panel and added extra mini heatsinks to increase the cooling performance, and have applied new thermal paste/pads to the cpu and gpu. I use a LG display at 2560x1080 overclocked to 75Hz.
However, with all new games, my system is limited to medium settings with <40 fps on most, and plenty of screen tear. I have used the included software with MSI afterburner to check what is the bottleneck on my system, and it seems to be the gpu. (I tested with metro exodus, and 100% of the gpu is being used, whereas the cpu stays around 30ish%, memory around 2.4gigs of my total 8gigs with medium settings).
I have been interested to mod my system further with an eGPU, as the laptop itself, while being dated, is still a powerhouse on most applications. I know that my laptop has a mPCIe slot for the wifi chip, which is what I plan to use got connecting said eGPU (Will be using usb wifi chip to regain wifi). However, very little info is available about the compatibility of external graphics cards for this laptop. I've read forums of a (weaker) laptop, the g75vw, and some people having successfully run cards such as the 780 ti/ 660ti etc.
I have already purchased the "beast EXP GDC v8.4d" PCIe dock in hopes of obtaining this feat. Due to recent terrible worldwide events, shipping will most likely be delayed for a couple of months, so I have time to research further. It's around $40USD.
I've heard that 1000 series (nvidia) cards will not run, due to driver incompatibility. However, I am looking to get a 900 series card, specifically, the 980 ti. Does anybody know if this card will work?
Also, my laptop has a thunderbolt 1 connection. Would this be a better choice?
Any help would be appreciated