I already gave you an explanation why this will not happens, you only need to focus in what i wrote.
Having 1 chat for all is useless since it will be flooded with no sense.
Having a personalised chat for 2 persons as you stated or even for a small group will not happens because it needs too much data. A forums where the members lists, general statistics in profile, who is online data...etc are all disabled to reduce data consumption, will not support your in-forum idea.
Am I wrong?
Anyway good luck.