Just a few Points.
1. Enhanced Aim: The first and the most basic enhancement, one will notice in Legions, while using Sky-Axis is, the ability to consistently aim at targets. In all our chasing days, we've found ourselves to be chasing the enemy flag carrier, and gaining more speed than he has. We would then be forced to slow down, and try to match his pace, as we just want to stay on his back, and finish him off. There would also be scenarios, where the enemy Capper is floating above us, and we can't aim perfectly, because of the limitation of the vertical free look. Therefore, when you apply the Sky-Axis, you will be able to tilt backwards(all the way, if you want to), without the vertical limit and aim consistently. Meaning, if you turn your head backwards vertically, to a 45 degree angle, you will gain an extra 45 degree aiming angle to the top.
Another, and probably a better example would be, when the enemy Capper is taking the same route as you, and is approaching you. There is a chance that, he will pass you, by floating above you. Therefore, by using the Sky-Axis, you'll be able to turn quite a lot, while still being able to shoot at him consistently.
Firstly, I have to say, I think this would just make things more confusing, you see, while you might be able to get those extra shots in during those moments, you've got to add on the time spent re-angling yourself, then add on the fact that You are also moving and have to be able to switch back to watching where you are going immediately afterwards. in terms of new players, it would make the learning curve steeper than it already is. In terms of experienced players, frankly, is the current system That bad? I mean, All it takes is a slight sideways twitch of the hand when passing the vertical view to keep tracking them, and it's very rare for them to be directly above you anyway, so chances are most of your tracking will be with a side-to-side mouse movement anyway. In this case, I personally would much rather stay at my normal angle and be able to take a few potshots then continue on my way, without crashing into the nearest hill.
That is why, it is effective for any player to make a quick 180 degree turn, shoot a rocket and turn back.
Here, by applying Sky-Axis, the player may shift the axis of the character, 45 degrees forward, therefore gaining an extra 45 degree aiming angle at his feet(note: it doesn't have to be exactly 45 degrees, as it is just an example, although the angle may be used to obtain the optimal balance between height and speed). He may then completely rid himself off of forward splash effect.
In this case it may be a useful thing, although I have to say, not one relevant to me. If you happen to have high ping, you can actually just aim down like the old days. Also, is the 180 degree turn That hard?
Such as; the vertical Overdrive limit, where when a Raider tries to Overdrive, higher than the usual 30 degree angle(maybe even 45, I'm not sure), the Overdrive simply breaks. You may remove the angular limit, and replace it with a time limit. Something similar to the amount of time given, when the player overdrives while pointing upwards. The player would then have time to perform, and complete such maneuvers.
You'll find it's not actually an angle limit, but an angular momentum limit. By pointing upwards you go against gravity, and quickly lose speed until below the 88 threshold. The same occurs for fast turns. In addition, there is a short (2 sec I think) period at the beginning of an OD, where such a limit does not exist, hence why we can maneuver the way we do at the start of the OD.
Another adjustment which could prove to be interesting is to let walls be acknowledged as Overdrive initiators, just as any other horizontal surface. This would not make it possible, for the character to simply Overdrive off the wall without using the Sky-Axis. So, for him to do that, the player, before his character hits the wall, must shift his axis in such a way, that the character's feet will touch the wall, when collided, and then he may activate Overdrive. I believe this will give way, to various new and interesting methods of Overdrive Capping(may prove to be useful to Cappers, when defensive deployments are introduced).
This i do find interesting, but I suspect would make some things Too easy on the cappers, as at least currently, the defenders can know where the main "starting surfaces" are, whereas with this the cappers could avoid ever touching the ground (except for at the flag of course) and could make things a bit difficult.
3. Enhanced Flight: By now, your mind should have grasped the basic idea of this ability, and if you're guessing it, this is basically the normal skiing, but with the use of Sky-Axis. Sky-Axis will now allow you, to actually dive into a slope, rather than just down jet. Therefore, with the help of the normal movement keys, this will allow you total freedom of flight, where your Up Jet and Down Jet, constantly switch places. This is all in theory, but this should reduce, all that long range parabolic, bunny hops, and let you move in directions without too much speed loss. More like Overdrive maneuverability, but with a much larger required curve, for speed maintainability.
I do have to say, all this would do is allow thrusting at points in-between up-upforwards, down-downforwards, and the same for back. Add in 360 deg of lateral rotation (i.e. what we have at present), and that's already a great deal of control. Adding a little more would be a very insignificant difference, particularly considering, most of the energy usage is more to do with inertia. Yes, if you're intending on going in one of the intermediate angles it would be slightly more efficient than alternating between the two closest angles, but considering the coding required, not to mention the additional learning required on how to use it, I'm not sure it's worth it.
Edit: Oh and yes, I do know a little about programming.