The MX can't be used to capture cartels, bounty hunter base is no longer a red zone and if it is being used to shoot at police or used wrongfully anyway, it will get taken away. It doesn't make sense as an illegal firearm.
A bounty hunter should be able to use the MX to bounty hunt with no problems from police as long as they use it properly within the law. It being illegal kind of forces you to be hostile towards police officers a lot more often.
If it will not be made legal, please tell me why. It was legal for years before and back then it was fine and could be used for cartels and such.