[SD] We would not assemble in this park
A: Nous, nous ne nous réunirions pas dans ce parc.
There is a Forum SD for this sentence, but it's a waste of time.
The skill 7.29 At Home has a dozen or so sentences where the subject is emphasized by repeating it with a pronom tonique. You can't tell that this sentence is looking for that emphasis from the English sentence. Nous ne nous réunirions pas dans ce parc. is therefore an alterative.
In the website Parlez-vous français, there is a lesson on Les pronoms compléments toniques, that explains:
Un pronom tonique s’utilise dans différents contextes :
Il s’utilise : pour insister : Moi, je suis française.
Madame LeGrande didn't give the technique a name, so I did more digging.
The site Le FLE pour les curieux says that this is a type of mise en relief avec un pronom tonique. But can I trust what they say ? I can't find any creditials listed on the site.
Français Facile, in their lesson on Procédés de mise en valeur, calls it a type of Procédés emphatique or Mise en valeur. It's the third of five types in the lesson.
The Bon Profs, in their lesson on Les procédés emphatiques, seems to say the same. Neither they, nor Français Facile, say anything about mis en relief.
French School TV gave a half hour lecture on mis en relief, which was great, but they didn't cover procédés emphatiques. I still don't have my answer on whether a procédés emphatique or a mise en valeur is a type of mis en relief.
Nous, nous ne nous réunirions pas dans ce parc. is straightforward, but how about saying the sentence with On ?
Soi is the pronom tonique when On means tout le monde, but for On meaning nous, the pronom tonique is nous. In her lesson Comment utiliser et accorder le pronom on, Madame LeGrande says:
De même, vous pouvez rencontrer “nous” et “on” dans la même phrase au registre familier. Cependant faites attention, cette utilisation est déconseillée par les grammairiens dans les autres registres. (Nous, on pense que vous avez raison.)
She doesn't say what to do for pronomial verbs. She says (Tu connais Paul ? – Oui, on s’est rencontré la semaine dernière.) is incorrect, but doesn't say anything about Oui, on nous est rencontré la semaine dernière.
I seem to recall duo accepting other sentences where I've used ON as the subject & NOUS as the COD or COI, but no specific sentences come to mind.
I still can't get a handle on whether Nous, on ne nous réunira pas dans ce parc. is a possible alternative. Duo doesn't accept it as a correct answer, but that don't mean Jack.