In my opinion, death traps could work in 2D gameplay, if the traps were located in both ends of an arena.

The falling cliff stage from MKD could see the arena getting increasingly smaller. Other stages with death traps that could work in MKX are the Nexus, the Yin/Yang island and the Shaolin Temple hallways from MKM with pillar traps on both ends.

The mine stage from MKD could either have two of it's death traps on both ends, with the third one in the middle as a stage fatality, or you could select which one to knock your opponent in like in Kratos' stage, when the match's over.

Now, stage hazards. Another stage I personally want back is the earth god's cave from MKM, and holes should sometimes appear on the ground, which the fighters could accidently fall into.

If the streets stage from MK9 returned, cars should sometimes come the fighters' way, and both fighters should risk getting killed, meaning, that even if your opponent's been run over, you must either jump out of the way, or destroy the car, in order to win. None of that should happen during throws, however, or the "finish her/him" parts.

In the Subway, fighters could be knocked in the rails, but it should also be possible for the knocked fighter to get back up before the train arrives. Characters with air throws should even be able to throw their opponents into the rails, if they're standing too close to the ledge.

All of this could make the gameplay even more exciting and challenging, imo. But since I know it could truly infuriate some players, there should be an option to turn death traps and stage hazards off.