The number one problem with a crewing company concept is the massive insecurity that the employees feel. Jetconnect pilots wake up every single morning wondering if they are going to have to start looking for a new job today. That level of continuous insecurity is massively corrosive on a personal level. They hate it, absolutely hate it with a passion. They leave as soon as they can get something more secure. A fixed term contract offers more security (except when a force majeure is declared, ie China at present, but they are by definition, relatively rare) as there is a known start and end point which allows for an orderly plan.
Never underestimate the psychic damage that the continuous corrosion of uncertainty creates. You would find pilots rapidly cycling in and out of such an operation, just as they do in Jetconnect. It will be a recency placeholder and cashflow generator between contracts.