Thanks,
Cronos !
Great mechanism (nicely adapted from FoG2).
Here is the progress of my testing for Dragoons (for the first 3/4 of the 17th century?) :
1) Mounted Dragoons
For now, I made Dragoons pure infantry on horseback, unable to shoot when mounted. And that lasts during the entire turn according to this mechanism (which is quite a disadvantage for a unit on the battlefield!). To balance them with the Light foot (such as the Detached Musketeers), I gave them Hussars' AP (20), making them able to move forward 5 squares while LF can move 3 square (and... shoot! during the same turn). Maybe it does not take enough into account the fact that, certainly, Hussars and such had better horses and were better horsemen, but AP=16 wouldn't give Dragoons a significant advantage compared to the LF.
30-50% Musket could be added to the Mounted Dragoons later, making some of them able to shoot on horseback.
2) Dismounted Dragoons
This is Vanilla Dragoons with only AP = 12 (instead of 16), that is the same amount of APs as LF.
12 APs (instead of the planned 10) enable dismounted Dragoons to evade.
I tried to balance LF and these Dragoons. That way, the dragoons can quickly move deep inside the enemy zone. When a too strong enemy force comes near the Dragoons, they can prefer to mount and flee without shooting.
I must admit I don't know yet if these Dragoons are of any interest/fun, compared to the Vanilla ones.

I must play more with them to know...
Any suggestions anyway ?