My flannels take me into the 60s. Once we get to the 70s I switch to lighter weight fabrics. In Chicago that means I wear my flannels most of the year.And, yes, it is appropriate to wear flannels with a typical blue coat. My preference is to pair a navy coat with a mid brown flannel.
I would definitely accept it. Over time, the replacement will be much more creased than that. It is not a defect, but a natural result of the leather being used. It is part of the character of the bag. If you don't like it, I think you should love for a different style bag.