Can we get the mana restore passive from Morello's back as part of Triumph or a new keystone?

> UNIQUE PASSIVE: Enemy champion takedowns restore 20% of your maximum mana

Some Champions actually relied on this a lot. And the reason it was brought back in the first place after the Athene Unholy Grail identity debacle, was because Mages would have no mana to do anything after a long team fight, forcing them to back.

I understand that Riot's answer to this issue is to just give mana items more mana but that totally just nerfed how certain items like Archangel's (Seraphs) scale, forcing you to buy more than 1 mana item that doesn't really mesh well with what the champ wants to do. Totally destroyed the play style of mana management and kill rewards., while looking into building other useful non-mana items for different purposes.

Edit: It's not that Archangel's (Seraph's) scale bad, but more of the fact that you have to wait much longer for it to become equal of power strength to what Morello used to be. Which kinda holds back some champion's early game power.