Cons would be cheap if they would scale better. 240 mp unit with 6 pop cap and 20 reinforcement cost is too cheap.
And the higher reinforce cost would be basic, upgrade or not.
If you buff a unit, you adjust it's cost if you have common sense.
What?
Cons cost 240mp.
Grens cost 240mp.
Cons have AI and AT nades only if you invest additional fuel and menpower.
Grens have AI and AT nades by default.
Reinforcing 5 cons=100mp.
Reinforcing 3 grens=90mp.
Cons don't scale at all into late game.
Grens scale really well into late game due to LMG.
What you have written makes absolutely zero sense.