Why not the FM2?
At least that way you won't get spoiled by the 20's
Or even the Hellcat to start beaning SA skills into yourself. "Same with the FMW"
The FM2 is very difficult to be successful in because of its speed climb and excel, if you are not in the vasinity of a general amount of friendlies you will get ganged pretty hard. The nik will add a more realistic measure of learning ACM rather than just flying a TnB plane that doesn't really take too much input to be a successful turner.
The spit 9 that Latrobe recomeneded is actually a really fun plane too. My personal favorite spit is the spit 8, which is also really fun. These are great low to mid alt fighters quick slash style fighters that can really mess people up. Suprisingly, and I don't know why, but everyone thinks the spit is a noob plane, but the vast majority of players do not fly it correctly in the MA. You need to be very aggressive, quick not fast, have a great understanding of defense tactics, and the correct time to raise and lower your flaps during a fight.
Many of the great vets of the game mass dueled and perfected their ACM In the spit 5 before they chopped it in half.