Simple solution to stop abuse from midlaners using support items.
Having all 3 support items unlocked by a support mastery [not key stone]. This mastery would also decrease the amount of gold you receive by farming but would boost your gold by generating it by all 3 know forms all together. 1- By hitting champions [gives more gold] 2- Being close to minions that die [small amount] 3- Passive gold over time [smallest amount]