Perhaps not as many controllers as now in NATS, each half would have half the compliment of controllers (as they would be controlling half the area) but with a built in pool of standby controllers (a percentage of the total that would be reasonable) to help take the strain in a short lived disruption of the whole. I'm sure that the unions and the accountants would scupper any such plan though. The disruptions are seldom enough not to cause a change in the system, it's just when it does the costs both financial and personal are huge. All the stranded passengers and the back logs this week will be remembered by those affected which is not good for business.