It’s possible because there are a couple of versions of ESP8266 that provide external antenna connector. If you have such need, please contact us directly as we can make OS3.0 top-level board using that particular version of ESP8266.
As it turns out, I didn’t need it. I was worried since my nearest wifi AP to one of my controllers, which is installed inside a weatherproof box, is about 110′, but I get a decent -75 db signal to it.