Strasbourg to Vienna Christmas Mkts and sightseeing

While in Strasbourg, I would not want to spend time going to Basel or Lucerne as a day trip. The markets are better in Alsace!
Colmar is great, and I would also try to visit a few Alsatian villages/small towns like Obernai, Barr, Kaysersberg or Riquewihr.

Esslingen could be tricky as a day trip from Strasbourg but you could visit on your way from Strasbourg to Munich. Store your bags at Stuttgart Hbf, take the S-Bahn to Esslingen. By the way, Stuttgart itself has an amazing Christmas market.

I cannot comment on your more easterly locations, for lack of experience.

You can't do all that in 12 days- or is it 12 nights? You have way too much on your wish list, and you're all spread out.
Start plotting out travel times between cities and prioritize the Xmas markets you are most drawn to. You don't want to spend most of your time on trains. Traveling between cities takes a minimum of half a day. Why are you flying in and out of Dublin? You could fly open jaw, (multi-city) into one airport and out of another. For example, fly into Dublin and out of Munich.
Have fun planning and start working with blocking out travel logistics. I don't see Switzerland fitting into this at all, as much as I love that country. Skip Fussen, just a tourist trap, IMHO.
Looking forward to seeing your revised itinerary.
Safe travels!

I've been to the markets in Strasbourg, Munich and Vienna. Here are my suggestions.

Depending on what time you arrive in Frankfurt, maybe spend a night there? The markets there are smallish but very enjoyable.

Strasbourg is great. We've been a few times, once during the holiday time. Three nights is perfect with one day spent visiting nearby markets in Riquewihr and Colmar. I've taken the train to Switzerland from Strasbourg, it would be a super long day and IMO takes away from the relaxing holiday time. Couple places we've stayed to consider: Hôtel Gutenberg or Hôtel Cathédrale.

You will spend > 4 hours by train to Munich from Strasbourg so your first night will probably be walking around in Munich. Figure one day to Nürnberg (it is only 1 hr away by train). Rothenburg ob der Tauber is about 3 hours each way from Munich. If you really want to go, it will be a lot of train time. If it was me, I'd spend 3 nights in Munich. Couple places in the city center we've stayed to consider: Platzl Hotel (I'll be there again in 2 weeks) or Mercure Hotel Munich Altstadt (good place with teenagers).

Have you considered spending a night or two in Salzburg? It is on the way to Vienna. It is a smaller city center. Last time we visited we stayed at Hotel Elefant right in the center.

Ahhh, Vienna, One of my favorite places. There are so many different markets scattered around the city, You could easily spend 3-4 nights here. If you spend an extra night, I'd visit Bratislava as well - it is only 1 hour away. The markets in Vienna and Bratislava are my favorites FWIW. I've stayed in Vienna a lot for work and have come to love the Hilton Vienna Plaza. Location is great as it is right on the Schottenring - right down the street from the huge main market and a short walk to St. Stephen's.

As you plan make sure the Christmas markets you want to see are actually open on the dates you visit. For example, Stuttgart opened on Nov 29 this year and Nuremberg on Dec 1. It would a shame to arrive a day or two early....

Thank you for the suggestions.