Battle SP and skills from other classes

As far as I know, after the first few levels, most people don't run around with a bar made of skills from only one class. So this got me thinking, why does only one class (your current) get SP and not the ones you used skills from.

Example, I'm a lancer and I've got radiance, cure, and blizzard from my conjurer class. If I use those skills, what if some SP go towards my conjurer class. If I then add second wind from pugilist, it could get some SP as well.

So what I'm suggesting I use skills from another class that class the skills come from gets a few bonus SP (10%?).

originally, you got SP for the use of any particular spell, and the sp went towards that class. Then everyone was glitching SP by not killing the mob and deuffing/healing/buffing and so on, on the mob over and over rackingup SP for each class for each spell. Thus they changed the SP gain to the system now.

The Armory System is basically a new way of having a character learn skills from the weapon. As you use the weapon, the weapon is teaching you new skills and techniques that it knows. If you're not using the weapon you still keep what you've learned, but you won't learn anything new from it.

FFXI was pretty much like that wasn't it? even tho you had one job your actions in battle would determine what atributes would rise, dodging would raise evasion skill, parrying, hitting with a polearm or casting magic would raise those abilites. your sugesting we have a similar system right?
that would be nice cause it actualy gave me the feeling of getting real battle exp besides the normal amount for that 1 especifc class that is holding that 1 weapon like we have now