Support Only Items
You could buff the support role by giving it the same treatment as the jungle role, gating their items behind a summoner spell.
This would prevent support items being abused by top/jungle. Knight's Vow, Redemption, etc would become items exclusively obtained by having the support summoner spell. The summoner spell should give 1/5 gold from minions slain by allies (not minions that die around you).
Summoner spell
- Invulnerable CC shield (self cast or ally cast a shield that absorbs all damage and gives cc immunity for 1.5)
With this summoner spell equipped, minions/monsters are only worth 75% of their value when slain by summoner with it equipped. Which means you're hindered if you take it top/mid/jungle.
&
, sometimes taking 
instead of the adc)
, he may be a jungler be he is designed to have a support playstyle, 
are pretty common on him because he is supposed to use them. That would left him the choice of either using a unadapted build or to sacrifice his 
. And riot don't like to make exception in the rules. Also, what about 
&
mid that might choose to build 
to help their team?
I don't need 
and RIOT forces you to take it to be relevant!