It's not hard when you move from focusing exclusively on the "I don't like it, nobody can & it can't be done" end of the pool & start looking at things that worked in past editions. Plate reduces speed & penalties to certain skills but gives high ac. Chain with some dex gives moderate to good AC but a minor penalty to some or all of the same skills Leather plus (lots) of dex gives low to moderate AC but few if any penalties to skills. Any of them can have some chance of causing spells to fail when cast while wearing it that is inversely proportional to the AC it gives while various classes & subclasses like EK & AT might give small cumulative reductions to that chance at regular intervals to avoid being an agonizing repelling EB type dip feature for what are otherwise pure casters. Specific armors could even give a reduction or increase in specific damage types taken like some of the 4e armors did.... Of course doing that well depends in some degree on admitting that relying on (dis)advantage as the first last & only option is an application of maslow's hammer
that fails to provide the precision & finesse needed for many areas of design*.
* There are quite a few of them already, these would fit right in.
You can have all those choices and more if you attached AC directly to the class.
War Paladin: 18 AC, 1d12 damage, disadvantage on stealth
Protection Paladin: 20 AC, 1d8 damage, disadvantage on stealth.
Peace Paladin: 16 AC, 1d4 damage, can cast sanctuary at will.
Dragon Paladin: 17 AC, 1d10 damage, 1d6 damage in a cone. resistance to your dragons element.
Blood Paladin: 15 AC, 1d8 damage. Gain THP equal to the damage dealt.
Fighter: you can swap between these as a bonus activity.
Range: 16 AC, 1d8, +2 hit.
Offense: 17 AC, 2d6 damage
Tank: 20 AC, 1d8 to hit
Skirmish: 18 AC, 1d8 to hit, you can move 5' after attacking and not provoke.