I know if these changes were made, coupling still spell with silent spell it could be a balance problem if magic was able to made completely undetectable, but it is the aspiration of any illusionist to conceal their magic to the point that it is nearly undetectable. I'm not saying that you would be able to cast magic and no one would ever notice, someone with spellcraft could possibly still detect the use of magic. They would make a check: their spellcraft + (wisdom bonus) vs. casters spellcraft + (dexterity bonus), and if they make the check they would get the usual "You guess <so-and-so> is casting <spell>", but those who fail, would be unawares that a spell had been casted.
To sum it all up, if you had both feats, and it was tweaked to be more efficient in concealing your spell use (which is what they are solely for
Also, this would allow counterspell, if it is fixed and reimplemented into the game, to have a counter so to speak. Thus, someone simply quicker than you on the keyboard wouldn't be able to counter every single spell you throw at them.


