You've listed much of the benefits it can bring about.

The real problem is there are many places like iobase.seek to modify
to support keyword argument, and seems not many people think it's a
good idea to do that, per issue 8706. But I think the former is the
main hinder. If there is one commiter that is interested to merge in
the related code, I might consider taking my time and handling the
rest related similar functions, including the test and the doc.