Just had a look at the qualifying to see which teams would be added if it was 32. From the top 4 teams of each quali group, minus all the teams who are actually at this Euros, the teams who would also be there are:
Netherlands
Bosnia-Herzegovina
Israel
Belarus
Scotland
Estonia
Finland
Montenegro
Norway
Bulgaria
Denmark
Serbia
That would take it to 36 though so 4 would have to be cut. Either way I wouldnt be a fan of seeing all that in the groups. It's bad enough with some of the dross that is there already
edit:
After these you're literally getting into the likes of Faroe Islands, San Marino, Cyprus & Liechtenstein