(B) You'll run out of useful information for Knowledge to reveal well before you max out the skill.
That specific issue is something I very well have accounted for.
Much like how not every level of a combat ability would give you access to new skills, Knowledge would past a certain point serve only to expand your Skill Slots when necessary.
I can't make any informed opinion unless I see what you have in mind - both where the alpha skills fit and the number of points in the ability needed to use them.
It's hard to really use the skills available in Alpha as a baseline, since many of them are IMO garbage to begin with, especially after the recent changes to things like Ignite and Contaminate.
As per my "<creature> Dive" comment, the idea is to have lot's of similar abilities that have varying flavor and power based on how heavy the investment to unlock them is.
What I have in mind is something along the lines of:
Throwing Knife (Assassin 1) - Throw a knife that deals piercing damage without breaking stealth.
Poisoned Knife (Assassin 2, Cruelty 1) - Throw a knife that deals piercing damage and poisons the enemy, without breaking stealth. Enemies already poisoned take additional damage.
Shuriken (Tactics 2, Assassin 1) - Throw star-shaped blades to slow down the enemy, gain 1AP when used from stealth.
Shadow Knife (Assassin 4,
source) - Throw a Throw a knife that deals piercing damage and become invisible. If you are already sneaking or invisible, you are not revealed and deal massive additional damage.
It ties in nicely into the skill crafting thing too, now that I think about it.
Since all of those are a flavored variations of the basic skill: Throwing Knife.
