T2Mobile is likely unable to meet our requirements. T2Mobile are not only designing the phone but even building/signing the firmware and device support code. Fairphone is putting together what they're given by Google (AOSP and GMS) and T2Mobile.

Fairphone gets to make high level decisions among the choices T2Mobile is willing to offer. For example, their move to T2Mobile with the Fairphone 4 coincided with the removal of the 3.5mm audio jack.