Not practical. As it is I source a special nodeMCU to comply with FCC requirements. Adding an external antenna is a compliance nightmare.
The nodeMCU has a pretty standard ESP12S module soldered on. If you are handy, you could swap it out for another with the antenna, but that would be the end of my involvement. There is a community of homebrew IoTaWatt folks out there, and they seem to do what they want, but I just can’t deviate from the current design.
Most folks with your problem add an external weatherproof external box. They are cheap enough and you can use rigid or flex plastic conduit for the CT cables. The good news is that the 1.5m cables on the Echun CTs facilitate that.
Again, the external plastic box is a better solution all around.