I'm don't think balance is necessary. It is true that to train one you need to train more skills than another, but that also encourages the majority of players to select the easier of the two. For those who do choose to train the harder tactic, they will often find that many teams are unable to deal with the kind of high value they have invested in that style of play. Most teams are not really prepared to do both things.
Exactly.
Even if more skills are involved in man marking, you can get a competitive UMM level with few skills, teams rarely trains skill points related to OMM and that can give you an advantage if you can grab it.
Last season, i won a WCC match against a team wich OZM level was waaaaaay to high, playing zonal marking against him was a suicide, so i had to improvise a team with a decent MM level, and it worked perfectly!
My point is that current UMM shceme is fine, you need many ability points to train zonal marking, but you also need many ability points to break man marking! Who trains jumping/heading on midfielders, for instance?
Usually, Midfielders are good braking zonal marking, while strikers are good braking man marking. When a team doesn't have that balance, he can be defeated with one specific tactic: the opposite to their whole team "O" skill.
