suggestion is to have caps on a summon contract
1) All summon contracts must only have a maximum of 9 beasts per contract with abilities. Any above this number should have no jutsu what so ever an be completly useless in combat
2) One summon must be the contract holder for that paticular summon group (this may be one of the non-combat summons)
3) There must be at least 2 child level summons. Such as Gamakichi and Gamatatsu
4) The contract should start with only one shinobi (creator), however others can sign the contract if the creator agrees to it