I’m introducing a group to Ars Magica—they’d all heard of the game but not played it. Two out of three of this group are generally more comfortable with storygames, and one of them was primarily interested in Ars Magica because of the shared/rotating GM structure. After our first session, they asked if it would be possible to have a flexible free-form magic system like Ars Magica in a Powered by the Apocalypse game.
I of course immediately said ‘no’, because PbtA doesn’t have difficulty levels, and doesn’t even really have rated skills in most iterations. Generally, either you can do a thing or you can’t, and if you can do it you do it just as well as someone else does.