I disagree.  It's a major feature of the revised IDLE that code is 
run 
in a fresh environment every time.  New users will only be 
'surprised' 
once, if at all.  They will learn to put the creation of the 
objects, 
etc. that they want to retain into the top level module they are 
running.  Getting into a discussion of whether to start fresh or 
not, 
and why, adds more confusion than it eliminates, particularly for 
beginners. Also, should this be implemented, if someone were to 
accidentally make the wrong choice they are going to be *really* 
aggravated!

I would accept a patch for a hidden switch to enable this behavior 
for the unique application in question.  Maybe even better, a patch 
for a normally disabled extension to add the functionality and menu 
entries.

Running w/o the subprocess is for 'experts'.  It was rather 
surprising we were able to continue to do it.