I agree we should consider hiring, but I think whenever the role’s vacant we should first ask in a cell if anybody’s interested. Like when @Fox went to sales, for some people it might be attractive for whatever reason. Plus, as we’ve discussed elsewhere in the past, our methods are relatively unique, so it will be difficult to find people that are more versed on them than we are.
Another plus is that when the assignee isn’t working out or isn’t happy, they have the option to step out into regular development without leaving the company. And vice-versa, when somebody isn’t happy developing, they can take “a break” and do meta-development. 
I very much doubt that unifying sustainability calculation, epic and capacity planning, inter-cell coordination and communication, sprint management (it makes sense to do that too), HR support, and recruitment for cells with a target of 10+ members will be anything but full time.
When I was handling recruitment for Serenity, I was already toying with the idea of making only that full time, let alone all the other responsibilities. As a matter of fact, I’m pretty sure that whoever takes on the full role is going to need help, from time to time. 