Legal issues aside, it'd be risky to put that much of the operation in the hands of multiple contractors who are obligated to do absolutely nothing more than to fulfill the minimum requirements of their business agreements with FedEx. We've seen contractors who post here and appear to be stand-up guys who aren't going to do more for FedEx than they have to.
FedEx needs a greater degree of control over things than a contractor model would allow them to have.
I do agree with your premise here on that risk, but honestly I can't say for certain nor know what they do and what they might be thinking. But I understand your point completely. Again as a customer, I'd love one pickup and your people to be employees. For example I can be in a meeting with your team and when talking ground we have some issues that need sorted and I come to find out the problem cannot be handled because X isn't allowed to talk to Y directly because they aren't employees. That isn't an ideal "get the job done" state, sometimes teetering on being a deal breaker. I'll assume business as usual until we see more, I do understand how unifying the colors though gets people thinking.