How was it coercion in the slightest?
Remember, in those days, daughters didn't succeed their fathers to thrones: they were simply given away in marriage to foreign princes or kings, and were then considered part of their married families, and their offspring too. The purpose here would have been matrimonial alliances. So under normal circumstances, had Chitravahana had a son, he'd have wanted to give Chintrangada to someone who could have made her a queen - a mother to a future king.
But since he didn't, he wanted his daughter to marry someone noble enough to be worthy of her, but not so high in stature that his son would automatically be expected to succeed him. Like had the proposal been for Chitrangada to marry Yudhisthir, that wouldn't have worked for Chitravahana, since any son of Yudhisthir would have been in the line of succession (say, had Pritivindhya and Yaudheya not been born). Which would have been fine had Chitravahana had a son, but not here.
W/ Arjun, he was getting everything he could have hoped for:
- His daughter married a prince, not some lesser kshatriya or brahmin;
- That prince agreed to his demand that his grandson would succeed him as king
What's more, his kingdom didn't take part in the war, despite the war involving the king's father!
The only downside, from a traditional/social POV was that Chitrangada wasn't able to fulfill her marital duties towards the likes of Kunti, Draupadi and other family elders. That didn't happen until the Ashwamedha yagna, when after the yagna, Uloopi and Chitrangada remained in Hastinapur w/ Arjun, Subhadra and rest of the Pandava family.
She would have done better to have had 2 sons from Arjun, and return the second to Arjun after the war, so that the Pandavas would have had a successor other than Parikshit w/o skipping a generation
I don't think chitrangadha s other son would have been considered because dwarak was more influential than manipur well as much as i know. So yeah prakishit always going to be the successor.
Yes had any of panchali s son survived things would have been different because panchals was a very influential kingdom too