Well first of all, I must say that I am very impressed with your suggestion, and I think it would definitely completely change the meta of how Valorant would be played, and it would definitely lead to a lot of novel and interesting situations within the gameplay. But I still think that having such an ability as a regular ability that is purchasable , with huge variation and unpredictability each time it is used within the game would likely mess up the game's delicate balance, and also the seemingly-arbitrary changes in the agent's hp can cause the player to feel that the game is being unfair to them. Having such an ability can change Valorant from a game where the effects of every agent's ability and weapon is predetermined and consistent, so the player's aim and tactics would determine the winner and loser, to more of a gamble to whether you heal or lose hitpoints is determined by the players around you and their skill level and decision making-things that are outside of your control, taking Valorant away from a game of individual responsibility and talent, and making it that if you make a mistake, you can offload that mistake onto your teammates or your opponents, which just doesn't seem fair.
Sure, there would be opportunities to use this tactically, such as by calling out and keeping track of your opponents hitpoints and using this skill strategically against them, but this also opens up a lot of opportunities to troll and make people upset, (such as purposefully using it on your teammates to weaken them and make them much easier to kill, so you get a second chance,) and and if players who choose this particular agent gets this type of selfish/wildcard reputation, the rest of the team might try to avoid them or not help them or back them up in fights, or worse: actively try to get them killed so that they don't have to worry about them unfairly losing hp, and since Valorant is supposed to be a team game, a team where all 5 members cannot properly work together would be devastating, and would most likely result in a loss for them, and this type of stuff happening repeating would lead to a lot of frustration and toxicity within the playerbase. If this continues, the meta might evolve, and people might actively dodge games or forfeit games early just because someone chose this agent which they don't want to deal with, so matches would be harder to find, more people would have to wait out the queue dodge timers, and it just wouldn't be a good time for everyone involved, and people would hate this agent, and Riot Games would either have to rework it, or remove the agent entirely because it is making Valorant a worse game.
Of course this is the worst case scenario, and the chance of my predictions and speculations all being right and the situation actually getting as bad as I described, is pretty unlikely. One solution is to obviously make the skill more expensive, forcing the player to save and give up some other advantages if they would want to use this ability, sort of like the high-priced but overpowered operator, and simply just limiting when and how often it could be used can address some of these issues, or at least make the blatant trolling less prevalent and gamebreaking, and also because psychologically, people tend to be more careful with things that are more rare. So I think that this ability would fit even better into the current meta if Riot implements it as an ult, since a lot of Valorant agents already have pretty overpowered ultimate abilities, and making Equalize* only usable 1 time per half can greatly reduce a lot of these issues, and also force players to save it and use it in only strategic moments that might win or lose a round of the game, greatly disincentives the players to use it solely to troll, since the opportunities to Equalize* would be rare, so they wouldn't want to waste it, and there would be a lot of pressure and expectation for them to use it to win the round for their team. Such an ultimate ability can definitely be completely game-changing in stressful and clutch situations when it matters, giving players the ability to completely turn the tables on who has the advantage, and I think that would be awesome, and that is how it should be implemented, in my opinion.
*Also yes I am renaming this ability Equalize because that is essentially what it is doing, and it makes more sense to me than calling it Equations.
