You are completely overlooking one fact - 6 teams using a Friday as their main race night DOES NOT mean that those teams will be able to race every Friday.
If Oxford were to be accepted as a Friday track, they would be bottom of the pecking order when it comes to having priority over that day. That means that they would have to use their alternative race night 5 times, when racing the other teams using a Friday. At present, this equates to half of their home fixtures being raced on 'off' nights if a team is wanting to race every week, in addition to KOC, Play-Offs being raced on 'off' nights too.
So your argument is flawed IMO