This would actually be an excellent exercise.
1. Select several vectors:
- Success as an underdog
- Overall trophies won
- Tactical acumen
- Tactical revolutionary (were their tactics transformative)
- Man management
- Player development (youth and adult)
- Club legacy (relevance within a club's history)
- Managerial/DOF skills (did they take more responsibilities beyond coaching, and how well did they do this?)
2. Assign relative weights to selected vectors. How important is one vector related to another? Maybe overall trophies is a 10, and success as an underdog is a 8, and tactical acumen is a 5? Whatever.
3. Rate a manager in each vector.
4. Find the weighted sum of a manager's score
5. Rank the managers based on this weighted score.