Armor without proficiency: any builds?

[FrancisBean]

Back in 3.5, I remember running across a niche build or two which relied on the fact that you can wear armor without having the proficiency, and was built such that the downsides were negligible. I'm wondering if there are any 5e builds which can do the same. I think 5e makes the penalty much more profound, such that it no longer works?

For reference:

If you wear armor that you lack proficiency with, you have disadvantage on any ability check, saving throw, or attack roll that involves Strength or Dexterity, and you can't cast spells.


Armor Check Penalty
Any armor heavier than leather hurts a character’s ability to use some skills. An armor check penalty number is the penalty that applies to Balance, Climb, Escape Artist, Hide, Jump, Move Silently, Sleight of Hand, and Tumble checks by a character wearing a certain kind of armor. Double the normal armor check penalty is applied to Swim checks. A character’s encumbrance (the amount of gear carried, including armor) may also apply an armor check penalty.

Shields
If a character is wearing armor and using a shield, both armor check penalties apply.

Nonproficient with Armor Worn
A character who wears armor and/or uses a shield with which he or she is not proficient takes the armor’s (and/or shield’s) armor check penalty on attack rolls and on all Strength-based and Dexterity-based ability and skill checks. The penalty for nonproficiency with armor stacks with the penalty for nonproficiency with shields.

Arcane Spell Failure
Armor interferes with the gestures that a spellcaster must make to cast an arcane spell that has a somatic component. Arcane spellcasters face the possibility of arcane spell failure if they’re wearing armor. Bards can wear light armor without incurring any arcane spell failure chance for their bard spells.

Casting an Arcane Spell in Armor
A character who casts an arcane spell while wearing armor must usually make an arcane spell failure roll. The number in the Arcane Spell Failure Chance column on Table: Armor and Shields is the chance that the spell fails and is ruined. If the spell lacks a somatic component, however, it can be cast with no chance of arcane spell failure.

Shields
If a character is wearing armor and using a shield, add the two numbers together to get a single arcane spell failure chance.
I can't remember the 3.5 builds anymore... It's been too many years. I assume they were casters who specialized in spells with no somatic components, but I'm no longer in the 3.5 mindset.

[Makorel]

I've never seen one. The cost of wearing armor while not proficient with it is just too high. I have heard of using heavy armor as a sort of improvised set of binds for mages, and also that a Sorcerer with Subtle Spell can ignore such restrictions. I think the best you're gonna get is when people are proficient with heavy armor but don't have the 15 strength to wear it without the speed drop and do it anyway for that extra 1 AC.

[Talionis]

Look at steeds for movement. This makes it better for small characters who can have medium steeds.

[JackPhoenix]

What you need is a way to make attacks without using Str or Dex, and without casting any spells in the process. That's actually doable: Either hexblade warlock (with Cha, but comes with medium armor and shields) or anything using Magic Stone (which uses Wis or Cha, depending on the caster, someone else would have to cast it and hand the stones to you, though). The later work best with rogue, as you still get sneak attack if you shoot the stones from a sling.

Also, the 3.5 builds generally depended on armor with low ACPs (which doesn't exist in 5e, penalty is the same regardless of armor), or never intending to use Str or Dex, and having a way to deal with spell failure chance... there are feats that ignore it for certain armor (those require proficiency, though, IIRC), magical armor or special material that reduce it (mithral chain shirt had no ACP and 5% spell failure chance, IIRC, and there was a magical property that reduced it even more), or not being arcane caster.