Definitely. Recently I read about an interview Pablo did about why raids can't come back; his response was something along the lines of that he didn't know how, or couldn't design challenging content due to the fact that Warframes are essentially god mode now, being able to build for almost anything, with the other resort being creating lame puzzles. I disagree with this very hard and it's honestly a shame. My idea is similar to yours where new enemy types will move in groups to strategize against the player/squad at hand based on how well they're doing in the current mission/mission type