I'd like a Stat-based Elite Four.
One that specializes in Defensive Stats (Similar to Shuckle, Steelix, and Milotic)
One that specializes in Offensive Stats (Similar to Rampardos, Alakazam, Machamp)
One that specializes in Speed Stat (Similar to Persian/Starmie/Electrode)
One that specializes in Health Stat (Similar to Blissey/Snorlax/Wailord)
Then a champion that is more balanced, or has one pokemon that represents one of each of the six stats as its main strength.
The type specialists are a must for gym leaders, but it seems like the Elite Four could be a bit more dynamic to emulate more of a trial.
There was something like this in the Norman gym in RSE where all the trainers had their own specialties and I think it worked out well. I think this is a good suggestion.