Very true also.
Galen and Krennic's history could kind of work if you go with the premise that Jyn is around 19 in R1, meaning that the opening events in R1 took place a few years after the conclusion of RotS. That would at least give somewhat of a window for Galen and Krennic to have established some sort of relationship. However, like you said, it was implied that their history dates back longer than a few years, but I suppose few years is at least something to work with.
The full fledged Empire was established at the end of RotS and it showed DS1 being constructed, so I guess you could pinpoint Galen and Krennic having began working together at that time or began to a short time prior to that, when there would have indeed been Imperial uniforms. That would have been around the time Jyn was born as well, if she's around 19 in R1.
