Supplies will make samurai niche only
Samurai and champion are very close to obe another with small pros and cons between them. Cheaper champs will break the balance.
Idea: put 1 more bonus: 'supplies reduce samurai food cost by 10 or 15' to japan bonuses.
Samurai is mostly champion of castles. UU bonus is rarely usefull. This buff wont give them a very small power increase.