It's not super common, but there are twenty or so cards that reference the stack.Cast it without paying its mana cost is more likely, they hate using "the stack" on cards.
IIRC at the the SDCC panel they showed this and said it was how morph was flavored in the world- the clans using 'ancient dragon magic' to disguise themselves. Sounds/looks kinda dumb to me, to be honest. A WHOLE BUNCH OF FIREBALLS COLLIDE ON THE BATTLEFIELD
There are a fair amount of vanilla/french vanilla morph guys that don't do anything, like ascending aven, spined basher and charging slateback. (I'm assuming by "face-up effect" you mean "when x is turned face-up do y," if you just mean they have some advantage a 2/2 doesn't have then you got me.)In Onslaught, the face-up effects always produced some positive effect, so your opponent is inclined to get rid of them immediately.
Re: Loyal Cathar. Though what I suggested is very similar, it would create interesting gameplay since you don't know what you're killing. Suppose it simply came back into play as a 3/3, however? It could give pause to your of opponent as to whether or not they should try to kill it.