Yes, Milan to Lake Como, probably Como is most convenient, and take the ferry around to different towns, Belagio, Mennagio, etc.
In Switzerland I highly recommend Luzern as a city. Wonderful town to walk around in, both day and night, plus jump on the lake boats and see the lake. Go up the Rigi or Mount Pilates for great views. Your wish list doesn't really allow you to go too far afiled for places like the Bernese Oberland or the Matterhorn. They are more west of where you are. But if you find yourself by Lake Geneva do go to Gruyere, the cheese town. Cute place.
Austria, well to me that means Vienna and Salzburg, and/or the Wachau Valley. Beautfiul cities that are easy for walking and much history in their own right.
All this takes a car though, using trains will eat up your time. If you go straight from Milan>Como>Luzern>Munich>Salsburg>Vienna it is right at 700 miles. Pick your hotels accordingly. You have the added bonus of seeing some of Bavaria, including Munich if you wish. On the way is the German town of Lindau too, and if you visit the old town on the island it is spectacular.