A railway user looking in to this wouldn't believe their eyes. It's very simple.
EMR have trains to run (most) of their services now. Keep them until the new trains are introduced.
Negotiate extended leases. Those responsible for late deliveries pay compensation to EMR to go to lessors. Part of that compensation moves down the chain to any company that has already signed contracts for future use of the trains, to include any company contracted for refurbishment work.
Any Open Access operator has no existing customers to upset. ScotRail's HST's are leased until 2030. Why should EMR and their long suffering customers have to take the hit when it's not their fault that their new trains are not yet fit for purpose?
All these cobbled together sticking plaster ideas are typical of MML in recent years. Just get on with electrification and introduction of the new trains PDQ. The legal profession can sort out the niceties of contracts. Possession is 9/10th's of the law