> > You can make the dictionary values as lists for the 'blocked'
> > argument for import_fresh_module(). That would work [for io].
> 
> I don't understand how having multiple modules in the blocked list
> will help in io case.  io.py will simply not work if _io is blocked. 

Which you avoid by giving an empty list of blocked modules, using
Alexandre's suggestion.

> I don't like that approach because it makes pure python code hard to
> discover.

Ok, but this code exists and it would be much better if it were
supported.

> The io/_pyio approach also prevents io.py from bring used by
> alternative python implementations unmodified.

It would be foolish to use it unmodified anyway, unless you like
low-speed I/O (and a JIT isn't a magic bullet).

The reason this was done like this is that the io module is imported at
startup: we want to avoid unnecessary parsing of extraneous code (and
unnecessary importing additional dependencies), and we also want to
reduce opportunities for failing to initialize the standard I/O streams
(especially stderr...).

> This will not solve the io issue, but will add some flexibility.

Which is pointless unless such flexibility is needed by someone.