Allowing people to, once every few months for real money, switch which class has a relic weapon by no means, NO MEANS, means that they would, should, or even consider cash shop boosts to clear harder content and the fact you're using that as a defense is frustrating, insulting, and purely idiotic.

In addition to this as I said before, who cares if people are paying for a very slightly faster relic via being able to que as a tank or healer? That means faster ques for all the other DPS. And for what? A relic weapon that may or may not be BiS?
Finally this has zero effect on people who as you say "want to do it properly" because guess what, the person getting this relic is also giving up one. You want more than one? Let's say he did "take advantage" of this and make it first on a tank? Seriously. Give me one legitimate reason why it would be game breaking and unfair for him to que as a tank if he so chose to to save a tiny bit of time despite the time gate? You've yet to do that.