In an ideal world I don't think anyone would have a problem with a second BLU being made, but time and resources are not infinite. Meaning if they did as you asked and for 6.0 made a second version of BLU that was unrestricted it would be taking the place of a different job. So for those people who either don't care for or are indifferent towards BLU and even those who just want variety or have a favourite job of their own in mind, their being asked to accept BLU taking up a second slot that could have gone to a different job.