Ending the sightstone tax for supports

I think one of the biggest reasons support is so underplayed is because of what I call "the delay of agency".

Because supports have slower gold generation and have to sink 800g for a sightstone as early as possible, they lack the ability to get power spikes at the right times.

Now, as a support main I am not a fan of the idea of giving supports the same amount of gold as other roles and giving sightstones for free as I've seen suggested elsewhere.

Rather, I want to propose a more elegant solution that won't result in Rengar support dominating the meta.

I think that masteries could be a solution for the sightstone tax and create meaningful and interesting choices for supports without changing how vision works too drastically.

My suggesting is that in each mastery tree there should be a keystone mastery for supports that gives supports access to special trinkets and also a (slightly weaker) bonus related to damage, utility or defense (depending on the tree). I think this tree-specific bonus should be weaker to disincentivize other roles from taking this tree.

For example, in the cunning tree, the 'support' keystone mastery might be something like (obviously play testing would be needed):

Windcaller's blessing - whenever you target an ally with a shield or a heal or apply hard CC to an enemy you restore [level adjusted value] health and mana. In addition, you gain access to support trinkets.

Example 'support' trinkets could be (obviously play testing would be needed):

Eye of the oracle - starts as the yellow trinket, but can be upgraded into an "oracle's sightstone" at level 3. When you use the upgraded form, it activates a sweeping lens effect where you place the ward, allowing for counter warding. The upgraded form otherwise functions as a sightstone.

Eye of the farseer - starts as a yellow trinket, but can be upgraded into a "farseer's sightstone" at level 3. When you use the upgraded form, it is like a blue trinket, except it stores 3 charges like a sightstone, allowing for safer, but less reliable, warding.

Eye of the augur - starts as a yellow trinket, but can be upgraded into an "augur's eye" at level 3. When you use the upgraded form, it is a sightstone with a maximum of two charges, but the charges refresh on a cooldown AND when you 'back', allowing for more consistent warding without having to worry about backing as often. However, it does not give the advantages of sweeping or the safety of long distant wards.

Thoughts? I think this would be a decent way to allow supports to not be delayed in their builds without breaking the game in terms of vision. The payoff would be a slightly weaker capstone.