Allow variations of the Data/MC plots

[MoAly98]

This is quite useful for many studies, where potentially Data/MC is the only quantity of interest, but also one might want to plot

Data - MC or Data/AllBkg or Data-AllBkg/MCor Data/(MC-ABkg) or cases where one wants to subtract all backgrounds from data except one (bkg = notMyBkg), then compare to that one background (MyBkg): Data-notMyBkg/MyBkg.

There are also cases where one wants to replace data with MC, and compare to another MC, for example creating a pseudo-dataset...

How do I support these kinds of plots easily, and do you produce multiple plots or add ratio plots or just allow one kind at a time that replaces Data/MC?