TL;DR, I've been tweaking and playtesting an arcade mode lobby in Overwatch for a couple weeks now. I did my best to make it balanced and give every hero a reason to use them. Here's those settings and reasons why they are what they are.


Heros are broken up by speed tiers. These are basically a rough guide, you can adjust them collectively to different ranges as long as they're separated into different speed brackets (though any slower than 140% can't effectively melee for crap and feel incredibly sluggish) though my settings are tuned for the higher end. ie, either use the high or low end of the ranges for the settings for all of them.

280-300% - Bastion is pure speed and doesn't rely on any hackable abilities.
260-280% - Hanzo can wall climb and is unhackable; Reaper can wraith/reapersition. Ana can Nanoboost (purely for psychological effect since everyone's already one hit kills, even with the defense bonus.) All are exceptionally fast.
240-260% - Mercy can rez/glide, and Lucio provides team-wide increased speed.
220-240% - 76 can sprint to be the fastest in the game, but only while sprinting. Widowmaker provides wallhax.
200-220% - Orisa can use Halt to yank people to a predictable point or off cliffs and no-sells Reinhardt charges with Fortify. Junkrat drops 'nades on death and has a 50 second cooldown trap, meaning he can generally only place one per life. Dva can defense matrix projectiles and has a one-time hit absorption thing with being forced into pilot mode. (I've been wanting to test if enabling Self Destruct to allow her to re-mekka with enough kills would be imbalanced, since everyone can move so quickly and everyone has almost zero cooldown barriers it's fairly trivial to avoid it)
180%-200% - Tracer has blink on a small cooldown, meaning she can use it a little less than once a second, letting her blink-strike and evade, at the cost of being relatively slow. Pharah can jetpack and somewhat hover (She can't stay up in the air) and has the only other projectile besides Orisa with concussion rockets on a small cooldown. Sombra can hack to disable some hero's bonus traits (though others like Bastion and Hanzo aren't effected at all in practice) but that close range channeled effect leaves her open to being killed; she can also stealth to speed boost similar to Soldier 76; All three abilities are on a short cooldown to prevent spamming them. She also can pull off an EMP with enough kills, though it doesn't have as much effect in a game where people are dying and respawning so fast and again some characters don't even notice a difference to what they can do.
160-180% - Reinhardt has big sweeping hammer swings that can hit multiple heros with little aim, and can lethally charge fairly often which is why he's the absolute slowest, easy for significantly faster heros like Bastion to zip in and kill between swings. Winston's multi-target is the jump pack, on 4 second cooldown and Reinhart-like sweeping blows when ulting.


And the actual settings besides speed.
-Cooldown for non-specified abilities is 10%.
-None of the abilities that don't matter like self-repair or lucio's ult are disabled, because they provide no benefit.
-Unless specified, default settings.
-Ult charge percentages operate on the assumption that health has been reduced to 20% to prevent bulky heros from surving punches with damage reduction skills or armor. Less than that means everyone who has one constantly complains that their barriers are about to break.
-Damage is of course set to 500% done and taken; base melee damage is 30. The only thing that won't kill in one hit is a glancing hit from Winston's jump pack. (Which is good, he should have to basically land on his targets to kill them with it.)
-Game balance/map switch: After game. Return to menu: Never.
-Hero respawn rate, 50%. Capture/cart/score speed, 75%. Start: Immediately.
-Hero limits, 2 per team. Too many of some characters like Rein or Mercy are not fun to fight against when stacked too high and it reduces people settling into a dominant strategy single hero spam.
-Hero settings: Disable Genji, McCree, Roadhog, Mei, Torb, Symmetra, Zarya, Zenyatta. (You can't disable their alt-fires)
Bastion: Disable primary fire, reconfigure, tank
Ana: Disable primary fire, grenade, sleep dart (does damage, therefore kills, therefore verboten)
Hanzo: Disable primary fire, scatter arrows (lol) dragonstrike and sonic arrows (they do regular arrow damage, sadface)
Reaper: Wraith cooldown 25% (to prevent him from staying invulnerable too frequently) disable primary and death blossom.
Mercy: Disable primary fire. 300% ult charge.
Lucio: Disable soundwave, primary fire. Base movement speed boost is 1.3x multiplier; At 260% settings his base is 200%, at 260%, ~185%.
Soldier 76: Disable primary fire, helix rockets and tactical visor (it re-enables primary fire while active.)
Widowmaker: Disable primary fire and venom mine, 500% ult charge. (Adjust down as needed; Even at 500% she doesn't get much use.)
Orisa: Disable primary fire, 30% cooldown on Halt.
Junkrat: Disable pimary fire, concussion mine and rip tire, 500% cooldown on steel trap.
D.va: Disable primary fire, boost (Way too controllable; way too easy to kill everyone with), Self-Destruct if you don't want to try it, and Defense Matrix 500% uptime/cooldown. (For as little as you're likely to use it unless you're deliberately counter-picking Orisa/Pharah)
Pharah: Disable primary fire and barrage. Jump jets at 40%. Hover jets reduced to ~40% as well, enough she has to land and come within punching range. Concussion rockets at 35%.
Tracer: Blink at 30%. Disable primary fire and pulse bomb.
Sombra: Disable primary fire. Hack, Translocator and Stealth all at 40%. If you don't like the hacking aspect, disable it and EMP and boost her speed a tier.
Reinhardt: The reason why you can't just disable primary fire for all heros. :V Disable Fire Strike and Earth Shatter. Charge at 40-60% cooldown, tweak as appropriate, but too low and it becomes dominant strategy to spam it.
Winston: Disable primary fire. Jump Pack, 60% cooldown. Primal Rage, 200%.


Bonus: Theoretical settings I would add for the rest of the cast if they didn't have alt-fire, all of which would probably change with playtesting;
Genji - Deflect on, swift strike on moderate cooldown similar to charge, 250% ult charge rate. 140-160% speed. Likely that swift strike would be removed in exchange for amping up his ult and bumping him up to rein/winston speed.
McCree - Roll on. I wish Flashbang did no damage. Up in the 260-280% with the other almost-no-abilities guys.
Mei - Ice Wall, MAYBE Cryo. 220-240 if no, 200-220 if yes.
Torb - When all you have is a hammer (which swings faster than the average melee), you get to go 220-240% speed but with a 500% ult charge. 240-260 if you still can't set his gun and hammer separately.
Roadhog - I want an option for no-damage hooks so badly. As is, he gets Bastioned at 280-300% with no useful tricks.
Zarya - Self-barrier on a long cooldown, Projected Barrier on a modest one, 220-240%; unless melee damage doesn't affect her bubbles, in which case, another useless set of skills, bastion speed.
Symmetra would have the teleporter with a high ult rate charge. 240-260% speed with the other team-boosting types. Probably the one I'd want ot add the most.
Zenyatta - Fast-charging Tranquility for self-immunity and additional movement speed, which doesn't do much, so probably in the Hanzo/Ana/Reaper speed tier.