It will require a lot of testing to make sure all the buildings can still be shot properly, especially under construction aeon buildings. There's been problems in the past with certain buildings, and now this adds more degrees of freedom that probably were not taken into consideration before.
This problem has been fixed a while back, see also this pull request and in particular the pull request it links to. The changes proposed here do not impact aeon structures any different than other structures. As an example: the aim bones and the collision box moves with the structure as it is being tilted.
There is also the nice "feature" that indirect fire units, e.g. t1 arties, on sloped ground sometimes refuse to shoot enemy units inside their range circles because of some arcane turret rotating reasons.
When this happens is super unpredictable for a human, probably making heavily sloped maps anything but fun
This problem has nothing to do with the slope, it has to do with the weapon of the artillery being set to lead the target. This can cause the artillery to prevent firing because the target solution is outside of the attack radius of the artillery. The slope can amplify this slightly - but the problem itself is not related to the slope. For example, this is also noticeable with Zthuee (on a flat water surface) and moving frigates: because frigates move too fast the Zthuee just look. They usually never shoot at moving frigates, especially if they are moving themselves too.
The solution is to prevent tech 1 artillery to try and lead the target. The up side is that it would always fire. The downside is that it would be as useless to moving targets as tactical missiles are. But I'd argue they'd still be a lot better because t1 artillery has a lot more splash damage.
If it were up to me I'd prefer units that always shoot over units that don't. But this particular change is very balance related, and the balance team doesn't like the solution.