In its current state the 'Quality Check' plugin is unlikely to get any new features as its owner has moved on. This will only change if he returns or if somebody else accepts the non-trivial committment of adopting it.
Modify Epub is in a similar state except a few hardy souls have made small additions without fully committing to be the new 'goto guy'.
I suspect both plugins would benefit from a good overhaul and could be simplified/extended by incorporating the new functionality which now exists in calibre to assist with manipulating epubs (and azw3 and kepub) but which the original creator, kiwidude, didn't have access to.
I'm not criticising anyone for not stepping forward as I don't want the responsibility either.
I suspect there are many forked versions of 'Modify Epub' in the wild as people squeeze in their own functionality without having to get to grips with the whole beast.
What might be interesting is if one of the more able developers found it an interesting challenge to create a new framework plugin that handled all the basic functionality but hobbyist Python programmers (e.g. me), could follow some simple rules to create slot-in modules that 'make change X only' and which can be shared, i.e. plugins for the master plugin.