I think it would be a good idea if GFs cards are the exception to this rule.
GF are generally more expensive than regular cards and more scarce. Also with the latests bonus for ranked rewards gf cards are kind of losing value and utility (nowadays tournaments is the best use of them).
Overall I agree with the proposal even though it will hurt me (bye bye chicken, ooze, lv 1 fiends etc). I think it will be good for the ecosystem.