Motorskills
Explorer
Starting 8, 14,15,10,10,16 with Inspiring Leader, Medium Armor and Stealth proficiency.
Maxing Charisma first, Then going for Resilient (Con) at lvl 12 (your proficiency bonus is high enough at that level so you can reap the benefits). Then maximising Con or Dex to your liking.
You may also decrease your INT to 8, increase STR to 15 and wear heavy armor. No Stealth option, but if your teammates are uncooperative you can always equip the lance and protect your mount.
Played very similar build (character was a Half-Elf though) and boy it was fun.
He's now 12th, courtesy of Winter Fantasy, and he is such a blast to play. Inspiring Leader, Resilient, and CHA 20. I won't bother increasing STR any more, will likely dunk the rest of the ASIs into CON or something.
He gives out a ludicrous amount of HP at the beginning. Usually I give ten 'permanent' HP from Aid, and then (now) another 17 temporary from Inspiring Leader. While I don't actually take ten minutes, I always roleplay that bit, either encouraging, celebrating, or blamestorming, depending on the situation!

I went with heavy armour (early decision), and play him as a roadblock. It works....okay, I guess....although I imagine there are other constructions that could be viable too (including some of DEX/medium-armour option that you describe above). But AC20, with protection FS, even before Shield of Faith, and magic armour/shield, is pretty strong. (Now that my CHA is max, I might have to take another look at Compelled Duel).