Current evolutionary theory is normally taken to assume that there is no correlation between mutations and fitness. Now, take some appropriate measure of correlation (if there is no measure of correlation at all, it is hard to see what scientific meaning there is in saying that there is no correlation between mutation and fitness), and let E(c) be a theory just like evolutionary theory, but where the no-correlation assumption is replaced by the assumption that the correlation has degree c. Thus, orthodox evolutionary theory is E(0), while optimistically-skewed evolutionary theories (such as those we'd expect if Molinism is true and God exists, for instance) will be E(c) for c>0, and pessimistically-skewed ones will be E(c) for c<0.
It is clear that for c sufficiently close to 0, E(c) will fit the same empirical data as E(0) fits. Simplicity suggests that c=0, but the resurrection of the cosmological constant is a reminder that a constant can be very close to zero but eventually positing a non-zero value may be justified.
It is an interesting question as to what upper and lower bounds can be found for c, given a particular measure of correlation. It is also an interesting question what value of c gives the best fit to our observations. If the best-fit value of c is significantly positive or negative, that would lend credence to Intelligent Design (of an optimistic or pessimistic sort, respectively).
In toy situations, this is the sort of thing that is amenable to computer studies—maybe people have even done this? My intuition is that even small departures of c from 0 would produce very noticeable results. But of course it could be that c is very, very tiny, in the way the cosmological constant is.