Will there ever be a way to pick up the other starting/new specializations? That you can unequip your starting one seems to imply that you will be able to.
Under the thread, "Unlocking other specializations," the idea was that yes you can get an upgraded and other new specializations, but to encourage new playthroughs it will be difficult to do so.
To quote Finchy, (through copy+paste) "I do plan on both having unlockable Specializations, as well as upgrades to the one you start with. I don't want the starting Specializations to be easily attainable, or even attainable at all, in one play through, as it would result in players just hot-swapping the optimal setup for every situation, which would be tedious. Having those be unique encourages repeat play throughs as well. Any that are unlockable will be hard to acquire and will be different from the starting ones."