Concept: Passive summoner spell

Summoner spell actives are basically "press F to cuck", especially heal and barrier. So why not introduce a summoner spell that has no active, but a passive? When I was looking at old summoner spells that could be used, i saw that fortify already had a passive, which read "When fortify is ready to cast, you deal 9 bonus damage to minions." Clearly the tech is there, but how could this be tied in and still be balanced? My thought was , an unused summoner spell, that was removed from summoners rift, having a passive when it is ready to be cast. Something along the lines of: "When Clarity is ready to cast, you gain 100% mana regeneration, and 5% CDR." You would still have the option to boost your mana for someone like Ryze, Anivia, or Jayce to pick up a kill, and have basically a mini blue buff otherwise. It would be pretty niche as long as it isn't overpowered, but anything to reduce the use rate of is very much welcome.