...I thought of a good idea.
They should do what some other brands did when arriving in the US.
A two way method of teaming up with an established brand and selling the cars in some of their dealerships AND individual franchise dealers.
When BMW's MINI came to the US, some dealers were individual, while others were co-branded BMW/MINI dealers.
Same with Fiat. Some dealers are individual, some are in with Chrysler/Dodge/Jeep/Ram dealers.
The most logical way for DS would be a combination of individual franchise dealers and co-branded dealers with a partner.
Since the plan seems to be DS only, without Peugeot or Citroen, the best option would seem to be...Mitsubishi.
In markets that Peugeot and Citroen sell cars in, they offer some models that are rebadged/restyled Mitsubishi models.
The i-MiEV/Peugeot iOn/Citroen C-Zero, the ASX/RVR/Outlander Sport/Peugeot 4008/Citroen C4 Aircross.
Though the Mitsubishi dealer network isn't that big, the addition of DS to these dealers might encourage growth of the Mitsubishi dealer network, in turn growing the DS dealer network as well.
Of course, the best way to go along with that is if PSA Peugeot-Citroen was to help Mitsubishi develop new models for the US market as well, that they could in turn sell in their own markets as Peugeots and Citroens.
If this was to happen, it could help both companies thrive, if done correctly.
Just a little food for thought.