They would probably have done miracles if they had received Dewoitine D.520s from the Germans instead of the old MS.406s

Only few D.520s were operationnal in 1940 at the beginning of the war, it just entered in service and the more modern Arsenal VG.33 and Dewoitine D.551 came too late to participate.
It was the single French fighter that was not outclassed by the German fighters. Though some 20 mph slower than the dreaded 109s, it was capable of turning inside the German fighter, it was not devoid of armor and had a relatively heavy armament, enough to deal with any German plane of the period. The most numerous fighters were older MS.406 and Bloch MB.152 but the Armée de l'Air came out enjoying consistently positive kill-loss ratios against the Luftwaffe.
Vichy continued to provide D.520s to its Air Force and in 1942 the Germans seized most of them and several were given to Italy, Roumania and Bulgaria.
Some of these seized D.520s were transferred to two Luftwaffe fighter training units (JG103 and JG105). They were highly praised by Luftwaffe crews for their exceptional maneuverability. However, the accident rate was fairly high owing to the great differences between it and the German aircraft to which the pilots were accustomed.
60 D.520s were transferred to the Regia Aeronautica, and were operated primarily as fighter trainers by Gruppi 13, 22, 24, and 167. About a hundred D.520s were issued to the Bulgarian Air Force, which used them operationally against the US 9th Air Force. Most of these were lost in combat. The Rumanian Air Force operated a small batch of D.520s in combat on the Eastern Front, flying them alongside that air force's Bf 109s.
http://www.csd.uwo.ca/~pettypi/elevon/b ... /d520.html
David