You still dont get it. You dont have to buy jp4 preemptivly. You can just spam light vehicles, much like any okw player using spec ops and then if enemy deploys medium tank you are just 135 FU short of counter. Much like spec ops but even cheaper and doesnt force you to pick doctrine.
No, you're not. You're circa 600 MP 185 FU short of a JPIV, because you have to build Battlegroup for it. That JPIV then needs to have its flanks defended from both infantry and armour.
That's faster than the current 270 FU to get a JPIV out, but less than the 140 FU two Pumas would cost you.
And that's assuming you don't already have a Puma to counter
their light vehicles.