User blog comment:B214/Volume 22 spoilers/@comment-50.139.232.230-20160610182436/@comment-73.160.58.215-20160619042345

Issei is probably the only one to be promoted, for various reasons. As already stated, his prominence and achievements are too great. But there's also the fact that he already intended to go independent, and the fact that the First Gen Baal placed such a condition on his acknowledging Rias and Issei'so relationship. Akeno and Kiba have no interest in independence, so they most likely wouldn't choose to willingly accept another promotion and the expectations associated with it.

As for the "traditionalist" Devil's, at this stage and considering the huge blow to their reputation they received due to the Rating Game fiasco, they wouldn'the be getting in his way and would instead be trying to pull something similar to what they did with Sizechs and Ajuka in order to "leash" him. I don't think that they were all that opposed to his promotion in the first place. Rather, they used the excuse of having him go through the proper route of becoming a middle-class Devil first in order to delay the inevitable and give theme more time to "prepare for the storm" he represented. Meanwhile, the Satans also wanted to delay his promotion for Issei’s sake, to let him enjoy his youth as much as possible while letting him further learn about and adjust to Devil society.