Well, I understand and I share your view. It's a bad idea to change the game base because it changes the purpose of creating new creatures.
But I still think that it could be if the cost is balanced. Of course not with the abilities, but yes with the stats.
You want a 100/100 dragon? OK, when you'll be able to summon it, you'll be over.
The same with the oty. You'll have a big creature that can eat almost anything, but the cost is considerably higher so it will came much later and maybe is still better to put a plate armor on it rather than pay a higher cost.
On the example of the firefly. You'll have a unique card improved, the ones casted by the firefly queen will not be like this one.
But again, for me it's just a debate. Now I don't pretend to implement this on the game so if you want to close that I'm OK. If you want to keep debating, OK for me to.