Asking the real questions here.
I work in software development myself, specifically on the business side where we define new features and explain what they will offer to clients in terms of user experience. It is ESSENTIAL to put everything on the table and leave zero doubt when it comes to functionality. If you leave the slightest inkling of information vague around how something will work, you allow people to make assumptions and ultimately be disappointed in YOU.
Bioware - You definitely have known about this issue for a while, yet all communications from streams to forums until this thread have allowed the player base to misinterpret how the class feature would work:
People have been spending hours leveling new characters with the intention of switching classes, which they now cannot do. They can 'deal with it', or reroll and consider all that time spent a sunk cost. Some of these players have also probably spent Cartel Coins on in-game purchases, which they also need to now accept as a sunk cost. Subscribers get a secondary class that F2P players don't get, so in essence you've inadvertently made accessing a new class on an existing character a paid feature. It was NEVER communicated that playing new classes on existing characters would cost money. It sounds like the limitations around switching between 'mirror classes' for force users are tied to story progression, so this even impacts people that just wanted their character's aesthetic to feel correct for their character. Generally, when you create a new character, even though you get to pick your class from a wider range, you're stuck with it. Many of us assumed we would get to try out everything on a single character and stick with what we like.
So, to summarize, regardless of what your statements in this thread say, the way it reads to the players is "You can't do the thing you thought you could do for free, but if you give us money you might be able to."
Since I'm not sure, I'm going to apply Hanlon's Razor here, and assume you missed all of this out of ignorance and not malice. What I am sure about though, is if in my career I managed to disappoint to this extent with a new feature it would cost my company financially due to disappointed clients seeking business elsewhere. This was your most touted new feature, It's very much a big deal that you missed the mark by as much as you did, and whatever the 'technical hurdle' you encountered was, I hope for the health of this game you do right by its loyal playerbase.