I appreciate the work and thought that went into this, but this is not normally the kind of change that we apply.  Any change has a chance of introducing bugs (see, for example, issue 15109, where a seemingly innocuous change from % formatting to .format formatting caused a regression in 2.7.3 compared to 2.7.2).

The other option, applying it just to default, is also not normally done, because then the code base between versions is gratuitously different, making merging more difficult.

So, our general policy is that we do cleanups only when we are changing that area of code in order to fix a bug or add an enhancement.  And as you can see from issue 15109, even then we sometimes get in trouble.

Now, if you are interested in the maintenance of the cmd module, and can suggest one or more fix/enhancement + cleanup patches like Lucasz Lagna did for configparser, that would be wonderful.