I'd have no problem if he got rid of both and we start from scratch , in fact it's my preferred option.
Thelwell is far from perfect but he has had a negative net spend , reduced the wage bill and still given Dyche a slightly better squad than he had before. That merits some acknowledgement. However it's also right to say that the squad lacks balance especially in attack and full back.
I can see why TFG might keep Thelwell on.
However there is no case whatsoever for keeping Dyche on. Everything that he does inhibits this teams ability to play progressive, attractive, attacking football. The likes of him Pulis , Alladyce and Warnock are finished as PL managers , thank god.