BJ would have a chance in the first round and maybe the second. Don't forget that prime BJ was incredibly difficult to takedown. Randy Couture famously espoused this point of view. I also believe BJ had better hands than Khabib.
What would happen if Khabib took BJ down, thats one of the main questions. BJ had slick and unorthodox BJJ but Khabib is a monster. Could BJ manage to get back up...? Or avoid getting mauled? It would probably look similar to the second GSP fight, getting beat up by a stronger fighter with good GnP, if I had to guess.
Standing BJ has a good chance vs Khabib. BJ managed to give hell to a lot of fighters in the earlier rounds... GSPx2, Fitch, Diaz, Hughes, etc. Who are all WW and maybe similar size to Khabib.
Fan of all three!