Some basic ideas around mythic. First - please don't cap damage or take that approach. I posted a suggestion for how to rebalance difficulty for mythic that won't diminish any existing tokens or abilities. I posted that under Endgame's thread talking about difficulty.
truedungeon.com/forum?view=topic&catid=762&id=258332
As for tokens, etc for Mythic, I'd like to see the following:
1 - You qualify for mythic by having a Safehold 1. Considering the resources needed to get there, being the master of a level 1 Safehold makes you a "Mythic" adventurer.
2 - If you do a Mythic run, you get a different character card with your character being Level 7 (yes - skipping level 6 so one day the other tiers can have a level 6 option that wouldn't conflict with Mythic.) Ideally, this would include the class revamp - if not, just add on the 6th and 7th level elements that would normally happen via 3rd edition rules (casters getting additional spells and a 4th level spell, additional class abilities, etc..) Maybe even give martial characters (barb/fighter/dw fighter/ranger) a second attack with their main-hand or two-handed weapon.
3 - Players with a safehold 1 get a new lanyard that is golden or similar as an easy flag for DMs that the person has mythic tokens (and just nice to have for the players).
In terms of tokens, here are my suggestions: (all could be used in non-mythic runs)
Gloves of Sure Attacks: +1 to hit AND you are given your own golden slider that you can use and keep (normal size slider so not conflicting with Smak's.) It has your name printed on it and cannot be transferred to someone else.
Censer of regeneration: heal 5 hp/room and 2/run you can repair a dead PC body enough for it to be raised (fixing if disintegrated, sliced into chunks, turned to salt and crushed, etc..)
Meta Lenses: You can read the monster stats as if you were playing a video game on easy mode (only works in combat rooms.)
Boots of Flying: You can fly at will - no action required just regular movement
Achilles Armor: +15 to AC, armor is immune to being damaged or subject to heat metal, DR 2 against everything (including eldritch), crit dmg is reduced by 50%
Gem of focus: (treated as a permanent runestone and applied to mainhand focus item) +5 focus, +25% to overcoming magic resistance, and recover 5 levels of spells per run (split out however you'd like)
Book of Ultimate Scrolls: You may use scrolls as a free action, you can use any scroll of any level 2/run without turning it in and +3 to healing or damage from them
Quiver of returning: Arrows used return to user 2/day and +3 to missile attack to hit and damage