@Prium
Having more Professions on one character is a convenience. So why not just treat it like how Ascension treats other convenience items.
Introduce a DB purchasable [Tome of Professions #]
This tome expands the number of Professions your character can have.
As for the humanoid "pet" idea, they should just have that as an option at level 1 like [Tame Beast], [Tame Dragonkin], etc.
Call it [Hire Follower] / cost: 6 ap
The follower would have the abilities like most enemy humanoids. You can break them into (4) basic categories: Melee, Ranger, Healer and Caster.
Special NPCs/Followers would have abilities like: "Loot", "Skin" or "Pick nearby Herb".
As for the "Expertise" profession... I think the introduction of High-Risk recipes covers a lot of that. The important part of any profession is to make sure it remains viable and useful in the late game. More quests or world bosses that drop Profession recipes is always good. 🙂 The Callboard daily Profession quests was definitely a good move on Ascensions part.
As for flexibility; I wouldn't mind seeing professions being able to add "of the Bear", "of the Tiger" or "of the Owl" to raid gear.
I'm just kinda bummed that they didn't put the [Mythic+ gear upgrade system] and the [Tier Gear Token system] into the players' hands. It would have been cool if those gear upgrades required Tailors, Leatherworkers, Blacksmiths and Jewelers (instead of an NPC).