How much should addons increase a killers odds of winning?

In the interest of fairness and fun, I would rather that addons and the choice of maps doesn't make too big a change to win rates.

So IMO all maps should have average win rates (where a draw is counted as 0.5%) in the region of 45% to 55% at most. And the choice of items should make at most 10% change for survivors or killers also.

In a perfect world, SOME of the Addons would change the killer's power somewhat to afford them a different but still good playstyle, like Meyers staying at Evil 1 but gaining Wall-Hacks, or Freddy trading out snares for fake palettes. Bad examples of this would be the Chainsaw addons that make your 2 damage hit into a 1 damage one, or changing Doctor's cone into a narrow ring. It would be great if ALL killers had at least one alt-play option that might increase your odds of winning just because the experienced survivors wouldn't know exactly what to expect every time, and there'd be an element of surprise. These might increase your odds by 0% but they also might be 1-2 extra kills because people just don't know what to expect.

In terms of increasing their actual power, obviously the rarity of the AddOn should factor into the strength of the thing, however this is far rarer than one might expect. Stuff like "increase number of traps/hatches/knives held" are simple and straight-forward, giving killers more up-time without having to take as many breaks to equip up. Stuff like "extend reach of your attack" or "increase recovery time on your attack" are also great, because they make chases more reliable and, theoretically, end them faster. One problem, though, is that a lot of killers only have one option for these kinds of effects. Obviously Trapper can take progressively more traps, but Demogorgon has only a single option to increase movespeed while charging his leap. Generally, these help the core gameplay loop of "track, chase, down, hook, repeat" in one way or another, but are usually only maybe good for maybe a few fewer minutes in chase.

There are, however, LOADS of AddOns whose effects are completely imperceptible, or are loaded down with hindrances far in excess of what benefit they bring. It'd be like if there were Med Kits that increased your healing on the Obsession, but reduced your healing on everyone else (and you couldn't drop it). You've got stuff like 90% of Pyramid Head's options that increase your torment trails by one or two seconds, or give you one extra pulse on the killer instinct for walking on them, or try to give him Undetectable despite his movement and sword making so much noise that survivors can hear him coming from half the map away. These are all terrible. They usually do not affect the game in any positive fashion and do not belong in the game at all.

So, how much DO AddOns impact killers? REALLY depends on the killer. Bubba has great tools at his disposal, and Demogorgon is almost unplayable without at least Rat Tail, but Pyramid Head only has 3 decent addons at all, and they all just increase the reach of his shockwave, which is useless for pro players anyway, so they don't help him at all.

How much SHOULD AddOns impact killers? Based on the rarity, they ought to be either making your power better or your chases more efficient by tiers. The lowest might make you 5% better, while using purples and pinks ought to be making you 20% better. Remember: killers don't have re-usable items like survivors. They're AddOns only, and since they're single-use, the killer is basically burning 3,000-14,000 BP every time they equip some. Every hook is 500 BP, so even just using one brown addon requires six hooks to pay back. These things need to be giving you much more than a 1% boost to whatever you're doing.

I agree that Meyers is a great example of excellent AddOn design. He certainly has SOME that are no good, but he's got several that change up his game flow and several that just make him a bit better at what he does. And very few are suffocated by overwelming self-nerfs that make them totally pointless.