When you connect an external antenna, it effectively disconnects the internal antenna. At least that's the story; the internal antenna may not actually be "switched out" of the circuit. The intent of the external antenna is to take over for the internal antenna, which is frankly pretty wimpy, not to change the function of the base station.
It sounds like you want your AEBS to do two things at once-to provide local connections and a point to point connection. I really don't think that's practical, even if it's possible.