@Maverix 

Hi,

Is "AC1200" the exact model name of your router or is it just the class identifier?

On TP-Link's website I can only find the MR400, MR500 and MR600 routers, all being AC1200-class routers. Most of the available models (but not all hardware versions) have two detachable external 4G antennas and two internal Wi-Fi antennas (inside the router's housing). 

In case of detachable external antennas it is easy to connect extension cables and different antennas, however extending and replacing the internal antennas would require substantial rework.

@woozle 

I think the correct model would then be

"Archer MR600"

@Maverix 

The MR600 has external SMA connectors to which the 4G antennas are attached. Using extension cables to relocate the antennas should be easy.

I can't find any pictures of the inside of the MR600 router, but as I mentioned earlier, relocating the internal Wi-Fi antennas would require some effort. (basically, drilling two holes into the router's casing and install two pigtail cables with SMA connectors that can be mounted into those holes)