Wait, since when did the Pact of the Blade weapon do force damage? I don't recall reading that, and that seems like something that more of a big deal would be made of in general.

With the design I have in the OP right now, the only reason for full martial proficiency would be the same as why Hexblade Patron does under its design: patching levels 1 and 2 so you can be a gish from the get-go. That said, shillelagh on its own patches that, especially when made a "free bonus" action to cast by the invocation.

The way you'd gate Hex Armor wouldn't be by adding it to the spell directly and making it so that you get a slower progression of options; it'd be by putting it as an Invocation that adds new options to the spell, and gating the Invocation behind a minimum Warlock level. Either 9th or 10th; 10th if you want to force them to use an option to trade out invocations to get it as early as possible, and 9th if you are willing to give it a level early when it costs an invocation slot.

This also keeps Hex Armor as a Warlock-only feature, even if somebody grabs eldritch curse via a feat or other shenanigan. A Lore Bard who uses advanced learning to pick it up still maxes out benefit at a level 3 slot, and can't get Hex Armor from it.

In fact, I tend to think some Invocations of this sort are quite weak, so I might add three options with it. (This has the sneaky side effect of making it so that a Warlock casting out of a 5th level slot has 6 options to choose from and only 5 he may choose, making it a meaningful choice when he casts eldritch cuse.)

Rebuking Curse
Must be at least level 9 to take this invocation, and must know eldritch curse
When you cast eldritch curse, you may select from the following additional options to apply to the target when you cast the spell:
  • When the target hits you with an attack, roll 1d6. On a 4+, the attack misses instead.
  • When the target takes necrotic damage from any source, you heal the lower of that amount or the target's hit dice in hit point damage.
  • When the target makes an attack against you, you may make a melee or ranged weapon attack against the target as a reaction.


Dread Curse
Must be at least level 15 to take this invocation, and must know eldritch curse
When you cast eldritch curse, you may select from the following additional options to apply to the target when you cast the spell:
  • The target is Charmed and Frightened by you, and may make a Charisma save each round on his turn to end this effect.
  • You may Dash as a bonus action so long as your movement places you closer to the target than you started, or adjacent to him. You gain the movement capabilities of the gasseous form spell while moving, but retain your normal speed. To observers, you appear to move between blinks and when they're not looking.
  • If you have hit the target with a ranged attack since his last turn, he must make a Wisdom saving throw to be able to take any voluntary movement actions which end with him further away from you than he began his turn. This includes teleportation and other magical effects. Creatures immune to being Charmed are immune to this effect.