To make the Champion more appealing and the undisputed king of carnage still standing at the end of a big boss battle where he's bloody, hurting, and still looking to fight maybe make the following changes.
Lvl 3. Improved crit (19-20)
Lvl 7. Improved Remarkable Athlete
- same as written but also gives you
- +10' base movement
- Gain proficiency for dex saving throws
- move at normal speed while climbing,
swimming and over rough terrain.
Lvl 10. 2nd fighting style
- Greater Crit (18 - 20)
Lvl 15. Superior crit (17 - 20)
- gain additional use of second wind
Lvl 18. Survivor HP recovery is 5 + half your
fighter level rounded up.
- select 3rd fighting style
Lvl 20. 3rd action surge.
- Master Crit (16 - 20)
Optional at Lvl 20. May elect to forego 3rd action surge and limit crit range to Greater Crit (18 - 20) to select one of the following.
- +2 stat increase (can go above 20)
- +1/+1 for two stats (can go above 20)
- A feat of your choice
This makes the champion still a simple passive ability build, but makes him a lot tougher, a damage machine, and fun to play without making him to OP.