If things were adjusted once a month that should be adequate IMO. Others may think quarterly is adequate.
Is it possible to do this completely automated way, based on daily amount of fees which DEX collects? They don't deserve more than DEX collects, right?
Also, do all witnesses really deserve same wage? They do different job, like produce different number of price feeds, etc, don't they deserve different wage in this case?
First, lets narrow the discussion to what is possible without code changes, unless YOU are able and willing to write a proposal and carry out the work or hire those that can. Ideas that require code development at a minimum should be considered as a secondary option.
Second, you haven't described what criteria you want witness' individual pay to be based on. Unless you can provide more detail on how such a scheme would be coded, by what criteria AND make the effort to champion that thru the process, it's an idea without feet to walk IMO.
So lets get real and limit our discussions to practical solutions. Throwing out "wild" ideas to resolve this "Witness Overpayment" issue without adequate thought is not very useful. IMO we would be better served to decide what the pay rate target should be and simply state that as a policy. There are far more important issues that need developer attention that this.
But hey, if you want to put the effort in to flush out the details and write a proposal to implement and get the votes to approve it, I don't think anyone would stop you. In fact I would encourage you to do so and I'll bet others would too.