That we attacked with their JT first made them think we got less troops in the SE of the DMZ, so hiding the Ancient Cavalry was the right thing to do we see now.
I suggest to move forward the same Elite Javelin Thrower, to be named "Mortalizer" (COMA/DP) discretion, the Veteran Javelin Thrower, to be named "Dominator" and finally the Veteran Swordsman " to the tile between Wheat and Tobacco, and wait for the Brazucan Mount Doom Army to emerge from the jungle and go to tobacco or the grasslands NE of tobacco. Also move the two horsemen in the jungle SW of the tobacco and hide the rest. This may make them think we want to balance them out, nothing much more with cheaper forces, but even parity in the open.
Follow up one tile behind with 6 Veteran Ancient Cavalry, on the tile straight south of the JTs and the Swordsman, we keep the MDIs in East Point as a secret.
We need to maximize the gains of using these half obsolete troops as bait.
Hopefully, they think we want to face them in open battle with slightly more equal troops, then we ambush them with the entire might of the 6 Veteran Ancient Cavalry, followed up by Elite JT, then Vet Sword and then Vet JT, finally wrap up the battle with 2-4 horsemen if absolutely needed.
I know they gamble for GA, but let them bleed hard for it.