Currently py.ini allows to set default interpreters for python 3 and 2. i.e.:
python3=3.6-32
python2=2.7-32

But it is not possible to set a default interpreter on a specific version.
I.e. when running "py -3.6" it would be nice to set the default to 32bit. i.e.:
python3.6=3.6-32

Of course this makes only sense in combination with https://bugs.python.org/issue33922 as one requires the possibility to override the 32bit default then.