Circle line Germany centre/west

What does Frankfurt have that Paris doesn't? 

In contrast to Frankfurt, the largest airport in Paris CDG has a comparatively low level of networking with long-distance rail transport. 

This also puts into perspective the transport policy statement of the French Finance Minister Le Maire regarding the committed climate protection requirements, in that there are to be incoming and outgoing flights for connecting flights. 

No competition to TGV

Air France will no longer be allowed to offer routes within France that can also be covered by high-speed train within two and a half hours travel time. France's TGV network is very well developed and one of the fastest in the world. So, the national airline will only be able to offer flights between Paris and Bordeaux, Lyon, Nantes or Rennes to passengers travelling on transfer connections. 

Source: https://www.aerotelegraph.com/tgv-air-france-bekommt-staatshilfe-nur-wenn-sie-bahn-den-vortritt-ueberlaesst 

Compared to Paris CDG Airport, Frankfurt Airport has a good intermodal network. This is undoubtedly a positive locational factor, especially with regard to a more climate-friendly profile. 

In view of the current discussions and upcoming decisions regarding an improvement of the ICE network in Germany, a proposal with the working title "Circle Line Deutschland Mitte/West" is attached (see below). It would be conceivable to have 4 or 5 daily trains, both clockwise and counter clockwise. These should be the usual ICE trains, but with a variable dimension "Aviation Train Part", just like in air traffic with a business and an economy class. 

With a surcharge, this part of the train can also be used by more ambitious passengers without a connecting flight. It is a basic requirement that the service must be at least equivalent to that provided on a comparable flight. 

The usual air travel infrastructure is available at the corresponding airport stations, e.g. check-in counters or lounges. A similar infrastructure would also have to be set up at the non-airport stations on the Circle Line, i.e. in Kassel, Paderborn and Dortmund.  In addition, a comfortable electric shuttle bus should be provided between the respective main station and the airport in Kassel, Paderborn and Dortmund. 

The selection of the stops is a suggestion. The final design still leaves a degree of freedom, such as the question of whether, for example, in Frankfurt, Cologne and Düsseldorf there should also be a stop at the main station. This also applies to the establishment of a free electric shuttle between the main station and the airport in Dortmund, Paderborn and Kassel.