I was curious if there was a possibility of doing Class specific player companions? Perhaps putting in archetypes/feats/powers that haven't fit in other places, uncommon race favored class bonuses, regional differences between characters of the same class. To me it sounds like a viable option like the Race books.
I believe they've said no to this in the past, due to the amount of classes that would need to be covered, and the guarantee that players would be upset about having to wait so long for their particular favourite to be covered. Especially when you take into account that not every month's Player Companion could be aimed at a single class, so you'd get at most 4-6 classes per year getting the special treatment.
How about a bundling then? Paperback companion with 5 classes in it and rules meant to expand on those 5? Last check there were between 35 and 42 classes (depends on if you count the Unchained and Alternate classes...)
5 classes/month, you'd be done within 9 months tops.