I may be mistaken but the simple champion became quiet fun.

The core is the crit on 19 & 20. In order to optimise it we want to roll d20 a lot.

Species : Human to gain Heroic Inspiration after a long rest & Lucky

Background : Soldier because it works great on fighters and also to gain Savage Attacker which increase damage.

Fighting style : Two Weapon Fighting

Weapon mastery : Hand crossbow, light hammer, Scimetar and Shortsword.

Feat : mounted combattant for lots of advantage 

At range or melee,

At range or melee : Nick, Vex and the TWF will allow 3 attacks per turn. You can use additional d20 with Heroic Inspiration and Lucky.

 Later you take piercer to benefit extra damage dice from your critical hit. Then Crossbow expert to ignore loading at range.

Does it work for you ? I think heroic Inspiration from human will be wasted due to champion lvl 10 Heroic Warrior but will work well for 9 level.