Specifically assume that Slovenia chooses to remain in association with Austria but no other real changes. Even Fiume is grabbed by Italy after an abortive time as a 'free city'.
With the addition of Slovenia and particularly Slovenia's access to the Adriatic what might this do to Europe in the 1930s? I assume that the WWI Austro-Hungarian fleet is still seized by the Allies but something new might have been built.
Might an Austria with added wealth and population carry through the arms buildup considered in the 1930s, perhaps deterring Hitler from simply waltzing in or, more likely, could the arms purchases lead to some kind of association with either Czechoslovakia or Italy?