It isn't unfair in the least. People select planes for individual 'jobs' all the tme.
As much as people hate to admit it, the Spit IX and Spit V ARE actually two different planes, with totally different capabilities.
Adding in a Spit LF IX, at least the clipped wing version that was by far the most common of the Spit IX series, would be like adding a different 109. You aren't going to try to tell me that the 109g-10 and the 109f-4 are the same plane too, are you?
It really is puzzling to me why people hate Spits so much. Can someone clear it up for me? I'll tell you what they look like from my point of view. If I am in any 190, they are going to die. Or at the very least, we are both going to live. If I am in a 109G, they are going to die, or at the very least we are both going to live. If I am in a 109F, there will usually be a pretty good fight. If I am in a 109E, there will usually be an even better fight.
The Spit IX (and to a lesser extent the V) are the 'newbie planes' of our MA. They turn well, have good firepower, climb well, and dive well. Their level speed absolutely sucks compared to every other common plane in the MA. If you are getting killed 1v1 against Spits, you are making some serious mistakes. I'd be more than happy to go to the DA with you and try to show you their weak points.
Granted, in a 1 vs many, a spit has a much better chance to get you than say, a 109 does. But, in that case... YOU still screwed up by getting yourself in that situation to begin with. And yes, I understand that with some of the early war planes it is a hard situation to avoid, and I sympathize with you- but our MA is not an early war arena. It is a mid-late war arena. At least in most of the early war planes you can FIGHT the spit, which beats getting BnZ'd by a P-51, LA-7, 109G-10, or 190D-9 any day.