For reasons that I can't readily explain, I keep coming back to variations on modernising the Dewoitine D.500 series...
I wrote a long-winded backstory for this scenario but the short version is: what-if the initially feeble Dewoitine D.520-01 had been declared a complete failure and, as an interim, French decided to update their aging Dewoitine D.500/D.501/D.510 fleet. Here, the earlier airframes are rebuilt to accept shorter-span wooden wings and retractable undercarriages based on those of the experimental Arsenal VG.30 light fighter.
The première série SNCAN D.514 EC1s were rebuilt Dewoitine D.500 airframes to be employed by the Armée de l'air in the advanced fighter-trainer role. These were followed by HS 9 moteur canon-armed SNCAN D.515 AC1s rebuilt from Dewoitine D.501 airframes for a new attack-fighter role. The faster SNCAN D.516 C1 fighter was derived from D.510 components and similarly armed with the more powerful HS 404 moteur canon.
A proposed SNCAN D.517 for the Aéronavale was not realised. Instead, SNCAN began remanufacturing poorer-condition Dewoitine aircrafts for the more heavily-revised SNCAN D.518 C1. These most extensive rebuilds had reshaped radiator baths, taller tails, fully-enclosing canopies taken from the Arsenal VG.33 series, and other detail changes. Like the D.516s, the D.518 C1 were powered by HS 12Y-31 engines and armed with HS 404 moteur canons.
At the start of the WW2, many D.516 C1s were still in operation with three Groupes de Chasse. By May of 1940, some frontline D.516s were still flying as backups in regular D.518 units. However, by then, most D.516s had been transferred to the Escadrilles Régionale de Chasse replacing older types. A few D.516s were also transferred to equipment-starved Aéronavale squadrons after the German assault had begun.