The problem is that by the time of the PoD Champa is this tiny-ass remnant that can't do anything.
This was the territorial extent of Champa by the end of the eighteenth century-
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The Tay Son brothers had divided up Vietnam- the blue was Nguyen Hue and the yellow was Nguyen Nhac, with future emperor Gia Long briefly ruling the green for a while. See that thing called Thuan Thanh Tran? That was the remnant of Champa before your PoD rolls around.
By that time the Nguyen lords had essentially extirpated the Cham people from Vietnam, reducing them to that pitiful little state. Even if they had all the guns in the world the Cham couldn't break out from that. The land that had once been theirs was now alien to them, crawling with Vietnamese.
It's ironic that Vietnamese people cry foul to China but pay lip service to their own subjugation and virtual extermination of a people as well.
If you want a strong Champa, you'll have to go all the way back to the 14th century when Po Binasuor/Chế Bồng Nga unified Champa and was strong enough to attack Thang Long (now Hanoi).