If you can steal your opponent's knowledge, then you can steal their knowledge of some particular power. You would still need to be powerful enough to conjure said power and you would still probably need to practice using said power. A Jedi may have trouble conjuring dark side powers if they are not used to drawing upon negative emotions. Likewise, a Sith may have trouble using any power that requires compassion, serenity, etc.
You also have to think about morals. Anything that requires bending and twisting the Force to your will is something the Jedi would be unlikely to try. Anything that requires submitting yourself to Force is something a Sith would be hesitant to try.
There may be some latent/passive powers that simply cannot be learned. Miraluka's have no eyes, but they can naturally "see" through the Force. Iktotchi have a natural ability of seeing the future. According to Traya, the Force Drain that Nihilus used could not be learned, but instead had to be experienced. Strangely enough, Plagueis says the same thing about Force Lightning. Miralukas and Iktotchi may instinctively use their powers without truely understanding them.
Registered: Oct 2014
Location: France/Rezée (near Nantes)
So you are telling me that only a guy like revan could achieve this....?
Because it would requiere to be at ease in both side of teh force or be a pioneer in an othr way to be able to use the power stolen?
And what about sith magic, we can do horcrux with sith magic (AKA Darth andendu) why not eat soul like Shang Tsung do? It would be the solution, no?