Servants are banned or nerfed because they either force me to rail road a setting like gawain, have a hard counter on the enemy, and or have the chance to just screw up the enemy team who is already gimped by being forced to not auto kill players like they could be if say gae bolg was left unneeded.  Also jack is a death sentence to masters and servants as along with instant killing females at night she poisons people and masters with misty night and mind wiping the enemy team is bullshit.

Nasuverse magic has no set of rules however they have limits ship for example could magic copy roughly a handful of times without ton amping his power so without making a whole new system I'm limiting spells to be cast instead of turning this into some statistical bullshit system I would half was