Quote Originally Posted by Peasant Phill
You mean that I only should use FK if I'm on a tight budget. (That happens actually a lot more than in vanilla MTW)
The money differences are very small, especially so for annual support. My thought is that by picking the (slightly) better combat unit exclusively, the simplified unit inventory (being able to readily merge units, etc.) offsets any minute florin savings.

Quote Originally Posted by Peasant Phill
So NK replace FK and NFK replace FMAA ( as long as you can afford it)
Not exactly - I'd choose NFK to replace FFK, but FMAA are an entirely different (less capable, but much less expensive) class altogether. There's no reason I can see why both NFK and FMAA couldn't be used effectively together. NFK and FFK are much more alike, and having a little of both makes less sense. You'd benefit instead by having all of just one (preferably the stronger unit) type, with the ability to merge depleted units together into something stronger. Lots of depleted drib-drabs don't make for an effective fighting force.