Normally a character has to choose between wielding 2 of a shield, an arcane focus (or component pouch), and a weapon OR just a two-handed weapon. As a Warlock, I could choose to wield an arcane focus in one hand, and a weapon in the other.
I'm designing a Wood Elf Outlander Warlock who only has one hand (the other lost as a part of my backstory). This means I can wield NO two-handed weapons, and must choose between either a weapon, or an arcane focus (or choose to drop the weapon to use a component pouch).
What made the most sense to me (as a counter-balance) was to strap a shield to the hand-less arm. However, Warlocks and Outlanders aren't proficient with shields. This would require me to drop the shield in order to cast (A problem since unstrapping it would require an action, and burn a turn). Also, the description of a shield seems to indicate that a shield as 1 strap, and a grip that you hold to keep it in place:
A shield is made from wood or metal and is carried in one hand. Wielding a shield increases your Armor Class by 2. You can benefit from only one shield at a time.
Anyone can put on a suit of armor or strap a shield to an arm. Only those proficient in the armor’s use know how to wear it effectively, however. Your class gives you proficiency with certain types of armor. 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.
Obviously, I would need to be proficient with a shield for this counter-balance to work. I've considered a few possible ideas to try and have this, but I'm not sure they are balanced.
Just having the proficiency because of the lack of a hand.
Trading athletics proficiency for shield proficiency.
Having a custom shield which only grants +1 AC Instead of +2, while still being unable to use a normal shield.
Is there a balanced or allowable trade that would grant Shield proficiency as a starting proficiency for a class which normally would not have it, without creating an OP Character?
Hexblade is not an option in this campaign, since my DM is only allowing the original three patrons.
To clarify: I am asking for things you (as DM) have done, or (as a player) have seen done.