an overwhelming itinerary?

This is not a crazy itinerary because you have 3 night/2 day stops at many spots rather than rushing it further BUT I would suggest some tweaks and fewer quickie stops.

The first thing I would do is use that first jet lag day of arrival to get to my furthest spot and then finish the trip with 10 days in Paris. There are literally dozens of great day trips from Paris and Paris itself is barely touched in a few nights. It is more pleasant to not be rushing back a couple of days before the trip home. Rent an apartment and have a leisurely 10 nights/9 days. Do the trip to Rouen from there; it is an easy day trip and you can see what there is to see in a day. Here are just a few day trips we have done:
https://janettravels.wordpress.com/category/day-trips-from-paris/
In addition Auvers sur Oise, Chartres, Giverny, Reims, Rouen as noted, and many many more.

I think 4 nights is too much for Dijon but the idea of spending a longer stretch in Alsace with a car is great. There are so many charming villages, houses with actual storks nests filled with actual storks, great food -- just a great place to put down anchor and explore.

We often traveled for 3 weeks and when we did we would anchor with a week at each end (flying open jaw) and then do shorter road tripping in between. I like the balance of being in a place for awhile and seeing several things quickly. You of course know what feels good to you traveling -- but those are my suggestions. I feel particularly strongly about finishing with along stretch at the final departure stop --we have done it both ways and always regretted having to rush back to catch a flight. And the first day of arrival is a waste anyway might as well use it getting furthest.

Have a great trip.

When you are gone for a long period of time there are always lots of stops, so it can get very tiring. But, it looks like you have given yourself ample time in each place. It doesn't appear to be too much or too fast. For us, we have found 3 nights stays to be just about right, other than for large cities or places you want to see more like in Colmar and visiting Alsace villages.

On a one month trip we usually do laundry every 10 days, so unless you have a washing machine in an apartment, you might want to think about where to fit that in.

Check the length of the train trips and make sure you are happy with the travel distance.

Sounds like a wonderful trip!

We LOVE France!

This may be the first time I'm thinking an itinerary is too slow, instead of too fast like most of those we see here. Dijon doesn't need four days unless you're doing a lot of side trips besides Beaune -- like Vezelay, Fontenay, others in Burgundy. And for those you'll most likely want a car. Likewise Amiens, not that much there unless you do side trips, again driving. Rouen could be a day trip from Paris by train, or maybe an overnight, but not more unless again you're thinking of side trips into Normandy, where again driving would be best.

Which makes me wonder why you want to use trains so much (paying two fares) instead of just renting a car in, say, Annency, and dropping it in your last city before Paris. Driving in France isn't difficult (other than Paris), and you'll want a car for side trips from cities besides Colmar. The autoroutes will whisk you through your distance-travel days, and the car will give you flexibility and simplify luggage handling. Yes, gas and tolls are expensive and should be added to the rental fee, but it may still turn out to be a better value than rail fares. Try some scenarios with Auto Europe (for rentals) and Via Michelin (for itineraries).

Janet makes good points about concentrating your Paris time into a longer stay at the end. But we did have a wonderful trip several years ago with nine nights in Paris, then a couple of weeks elsewhere, then four nights back in Paris before flying home. The main thing is not to be rushing a long way from somewhere to CDG the day of your flight. Your present plan takes care of this, but an alternative, especially if you're driving, would be to get to CDG the day before the flight and spend the last night at one of the 4-5 good airport hotels.

This will be a fun and rewarding trip, but I think you'll do better with a car (outside Paris) unless driving is a problem.

I agree this is a driving trip. We are doing a month in the south of France in the fall and then a month in Paris and will have a car either leased or rented for the month. It is very hard to tour these areas without a car. We will do a week in a cottage in the Dordogne, two weeks in an apartment of friends on the Riviera and then a week road tripping with two or three night stops before coming into Paris.

Hi,

Great that you have four whole weeks for France. Good choice of cities and towns on the itinerary. Being "at the mercy of train travel" means that the option of a rental car is precluded? I would say that seeing Amiens and its surroundings needs a rental car, makes it a lot easier and much less time consuming. If you're into the history especially on WW1, spending the time in Amiens is worth. I first got to Amiens in 1989 as a day trip from Paris, have been back since a few times, probably totaling a week always a day trips either from Arras or Paris. From Amiens you could do a day trip to Beauvais, located between Amiens and Paris, not only for its famous cathedral but also there is a WW2 site in the town. In 2012 I went there a as day trip from Paris. No tourists go to Beauvais, not even French tourists.

Here is one more vote for moving your time in Paris until the end. Many of the things most people want to do in Paris require that you get there very early in the day to avoid long lines (as much as possible). If you do it at the end of the trip, you will be over your jet lag and can more easily get up early and walk for longer periods, which is more important in Paris than in smaller towns.

I agree with the suggestion for renting a car for this trip, moving Paris to the end, and adding Normandy and possibly Mont St. Michel. I would find 3 days in Reims to be a bit much, and would change out a few of these towns for time in Bayeux and Normandy, if that interests you. Usually you will find that the longer car rental ends up being a good value. Trains could be cheaper, but then you do not have the freedom of going on your own schedule and since you are already renting you might want to extend that.
Whatever you decide, it sounds like a wonderful trip