I read OP's primary complaint as being that check-in agents were not wearing CX uniforms.

It is quite common in Europe for carriers to contract with Swissport or Menzies for ground services at outstations, as it's very expensive and rather inefficient to hire your own staff to handle one or two daily flights. I don't know if this is a new development for CX at FRA, but it would certainly not be uncommon.