I also would not take many elements of the "Big" Games into Casual Games.
It would be an error to insert a complex story,
manyfold options, and complex character design. Casual gamers want fast-to-start and easy-to-understand
gameplay.
A good casual game should not need any or just very little explanation how to play it.
A trading simulation or RPG on the other hand should not be that simple,
to interest longtime players.
Also the biggest error is to insert "great-looking" grafix, shaders, models etc, because this just
leads to a slow and choppy game on a large porting of casual game customers.
(many forum users here think that good-looking grafix are shaders, and 20K poly Models..,
this is the wrong approach for casual games)