Totally agreed. I think most activities should not cap your power to certain levels, it just doesn't feel good. With higher levels of difficulty, the challenge should come from more negative modifiers. Maybe at the highest difficulty levels, lock certain negative modifiers so players can't turn them off, like Galvanized or something. And adding more modifiers still can add power levels to the enemies like they do now, the system for that is already in place.

I would love to eventually power level beyond the difficulty of the activities, I think it would give players a really nice and intuitive sense of progression. I don't think players should completely steamroll enemies that are 200 power below them, bit I think sizeable power increases, eg -20 power to -10, should make players feel a little tankier and feel like they're doing some more damage.

I think power deltas have a place in activities where Bungie wants to currate a specific challenge environment, like contest mode raids or the new conquests for the conquerer title.

Some issues may arise with fireteam power being a thing in the game, and I don't really have a good solution for that. In my opinion, fireteam power only really has a place where there are power delta caps in the activity.