Not so sure about that. I mean you can't move fast with a rifle shouldered, so are you saying that the only speeds should be sholdered/IS and sprint? I can see that being very fustrating.
How about we keep the current hip/is system (although with something added to make hipping harder, maybe even just not allow it), and then replace walking ( which no-one ever uses in its current form) with shouldered weapon.
So most of the time you run around like normal, and right click or whatever to raise IS, then if you are going to clear a room, you hold shift to raise your wepaon up, reducing your speed but making less noise and easier (MUCH easier I hope) to shoot.
Personaly I think hipping needs to be kept for smgs, and probably rifles too if they can find a way to make it very very hard and very random, so basicaly impossible to get good enough to rely on it like many do in RO:O. But I would rather see hipping for rifles removed totaly than kept in its current form.