As much as I want to see BLU and RDM in this game I don't think they can fit it in without compromising what made them what they were, much like SMN, unless you made them Tanks to justify the healing skills but that would enrage the faction of the playerbase who don;t want all sword users to be tanks (thought that's for RM and thus irrelevant)

Spell Glamour might work to persevere the feel of BLU, but the present (Egi-Glamour) hasen't even been implemented yet an even if this was a thing it might still fail because it wouden't change in effect. (much like Egi-Glamours)