I think the title sums it up, I was planning on using the Doomsday Engine for this but was unsure due to the fact that it allows for full degrees of motion when aiming, same rules apply to shooting, You can still aim in an enemies direction and shoot them when facing, for example, at the floor. (Best example is in Hangar with the imp on the cliff. In regular doom, you can just aim at the wall, that rule still applies to the Doomsday Engine). The engine also adds the ability to jump which you can just hotkey away.