Richard Branson does business with the motto "protect the downside" meaning that you need to minimise your losses if it all goes wrong.
£2m compensation for Martinez could turn out to be a lot of money if after 6 months or a year we choose to part company. He's known for his loyalty and will probably want a longer contract than either Periera or Rangnick (who will accept that moving to a new country is a risk). And the longer the contract the more we'll have to pay him to settle it if we sack him. Plus Martinez is already on Premier League money and he's in demand, if reports of interest from Malaga and City are true, so he could be the most expensive option.
Rangnick might accept a consultancy role on a rolling contract. Alan Nixon of the Mirror very often makes stories up, but it could be a good idea for the German to be head coach of Neville, Stubbs, Weir and Ferguson. He could mentor the four of them with a view to the most promising candidate taking over in a couple of year's time. If it doesn't work we could reduce his role or replace him.
It's a more continental structure but there are no obvious candidates for the job at the minute, so why not develop our own man?