The normal commercial way to handle this is to say you are completely independent and not Orcats-raiding current fares. This gets you the approval from the ORR. You then start, get the buy-in from some influential MPs etc about cheap fares, and then say you aren't making money and will have to withdraw the service unless you are let in to regular ticketing, completely forgetting to mention you started off saying you didn't want it, and if you are "forced" to withdraw the service it's all the ORR's fault for not letting you in ...
One very much hopes the operator does not charge people with valid "any operator" tickets again, and certainly not charge penalty fares. It is their responsibility to come up with an approach to check everyone has valid tickets before boarding. If they want to be like an airline, be like an airline. Maybe they even get fined by the ORR if they let anyone on board without a valid ticket. That's what happens to airlines.