I love your thinking, and can get on board with the mindset. Some of the questions can be answered, but depends on multiple values being addressed as a combo.
- Decreasing marking can work if it's paired up with the right Sprint/Acceleration and Line Length discrepancy.
- Stamina depletion/conservation is primarily based on the acceleration value. Lower acceleration = more stamina and higher acceleration = less stamina. The problem you run into is the very fast look of the game with a higher acceleration, or if it's too low you see little effect to players' fatigue levels.
- Decreasing team width would be relative to marking value. If you decrease it too much, with a lower marking, it could work, but it could also result in absent minded defending, or worse ADD (attention deficit defending). If marking is too high, then they'll try to mark too many players at once. From what I have seen, width may again be only for the offense, and not the defense. Similar to how it was when 1.05 patch came out in FIFA 16.