Ah cool I get you now, but it might be a bit tricky to implement nicely. If only half your body is visible but a "successful shot" is aiming at any part of your body it would then always be a max 50% chance to get hit which can then be silly i.e. why aim at someone's leg when you can't see it if you have 100% accuracy.
Typically you aim for what is visible and then from that the centre of it.
And that's why I think a larger "success area" combined with volutar's "always aim for the center of the visible area" would make a great shooting/cover mechanic.
You should always aim for the center of the visible area, but cover will make that area smaller and if you can make your visible area smaller than the success area, success shots may hit cover = cover is relevant. The problem now is that the success area is so small that it is almost impossible to obstruct so much of your area that the visible are is smaller than the success area. Aiming for the center of the visible area will almost always ignore cover. Increasing the size of the success area fixes that.
It comes down to two different reasons for flanking:
1- Shoot at your target without giving it cover (= increase chance to hit). This works regardless of where the target is looking, but the direction is given by which side of the target is protected by cover.
2- Shoot at your target from a direction it's not looking. This is independent of cover and will reduce retaliation (= increase your survivability) and also allow you to hit side/rear armor (= increase damage).
Ideally both mechanic should be in, but #1 is already not really potent currently (playing LoS shenanigans is more worth it than kneeling behind cover) and it will be worse after volutar's fixe, hence some of us being worried.