So, the thought I was having about that it that means that it's harder to unlearn a skill than it is to learn it. Specifically, sure, a fighter can unlearn a prof and it's underlying crits in one event, but it takes a templar two events to unlearn the skill, and a scholar even longer? That just strikes me as weird. It also means, as was noted in the original suggestion, that you end up with a great deal of flux in cards at the lower levels. From a storytelling perspective, it strikes me as disruptive that you can show up to one event with one whole set of skills, then at the next one be completely different. Even in the next couple of events, your skillset is subject to some heavy fluctuation. Keeping it at one skill per day makes it a more gradual shift, and is easier on a logistical level - they're already looking at tags and manipulating your character card as it is.
There are a lot of pieces to what you said, so I'll respond to the various pieces individually.
Assuming the 15 build suggestion, it is never harder to unlearn a specific skill than it is to learn it. You never gain 15 build in a weekend (unless your first ever weekend is 4 days long or longer).
As for how long it takes, I'm okay with a fighter taking less time (effort) to unlearn a prof. It took the fighter less time (effort) to learn it in the first place. Comparatively, different classes are unlearning at a rate that is comparable to the rate they learn.
The low level flux is a reasonable concern, but I would counter with two things. 1) I doubt many low level characters will try to take advantage of this, especially since you still need teacher cards to make it all work. 2) Characters simply don't stay low level in the Alliance system for long (depending on your definition of "low"). Given the fact that most players NPC before bringing a character in (thus it doesn't start at 1st) and most players get monthly blankets from goblin stamps, true low level characters are few and far between because they tend to start higher (than in the old days) and progress faster.
As for the last point, I don't think it is any harder for logistics to remove 1 - 2 skills (as a player requests), than it is to remove the specific set of skills (costing 15 build or less) that a player requests. I am pretty sure that is roughly equal complexity.
My final comment isn't a direct reference to anything you said, but more of a mindset statement. I am of the opinion that if a player isn't enjoying the way they spent their build, the Alliance should make a reasonable effort to fix that situation. The current system is designed based on the classic D&D early edition mindset of "you have to live with your character creation mistakes." Many people scoff at MMOs for catering to players on character creation decisions (with things like respecs), but it is a decision based on trying to make the experience as enjoyable as possible and not to "punish" players for a lack of system mastery.
15 build per event is still pretty slow if you are level 30, but at least it isn't molasses. If you aren't enjoying your character build, you can change it completely in about 3 years (roughly 1 year per 10 levels). Even at 30, you will be transitioned far enough in about a year and a half that you should be less frustrated (and odds are that you actually like at least a portion of your build choices, so probably faster than that).
On the other hand, 2 skills a game is molasses. At that speed, even a level 10 character (which I think this system is near the sweet spot for my recommendation) would take almost 3 years to transition and anything beyond that might as well be infinite time. That is not, in my opinion, a system designed to improve player enjoyment of the game. The transition is slow and often frustrating. For example, an orc fighter would give up a prof and a crit attack and wouldn't even gain enough build to learn read & write. Thus, the character simply lost skills with absolutely no benefit after one event. Part of the advantage to the system I suggested is that it tends to provide tangible benefits every event (every two events at worst). Depending on the transition occurring, it could be almost a year before a player saw tangible benefits with only 2 removed an event.
-MS