On the issue of paying "subcontractors" directly. While many if not most construction projects are set up with a general contractor with subcontractors under the general, not all are. Other projects like the Children's Hospital are set up with multiple trades as prime contractors with a construction manager to coordinate all the prime contractors.
I believe that the most recent projects at Jack Trice were set up this way. And it can work well. But the contractor who might usually be the General Contractor has no financial leverage over the major other trades (electrical, HVAC, plumbing, etc.).
At the Children's Hospital, as I understand, part of the issue was that the hospital would hire new staff that had different ideas on how things should be organized and designed. And the management staff would acquiesce to their desires requiring redesign and change orders. Changes during construction always coat more.
Also under a construction manager project, it is up to the construction manager to very clearly define what is in each contract. If this is not done well you can end up with gray areas between contract work where no contractor claims to have bud that work and the owner ends up paying a change order for that work.