Simple: have other spawn points for the ins apart from main at the start of the round. for example: Al basrah for ins should have spawn points around the map to simulate that ins are already there and not comimg out from a magical base. That gives the Ins the speed advantage of being ready for an ambush to the regulars.   This was done back in PR for the taliban and the insurgent faction . That would make total sense , it's their homeland and they're the ones defending  therefore they should be there first.
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