Well, I was trying to keep Patron and Pact being noticeably different in my posts.

The original Hexblade was "curse a foe" with Pact Variants. And like you said didn't really make sense outside of Blade Pact.

With my "Curse Pact" available to all Patrons, I was trying to keep to the original "this is a Warlock thing" idea.
This way, the PC could have GoO's Thrall and Curse; but not Thrall, Curse (spell), and Blade/Tome/Chain.

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But, if you're cool with anyone being able to get it as a spell, and Warlock Invocation giving additional options to it - go for it.
I'll be checking for your updates on that.

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I figure it'll take at least a month to test the "Hexblade" changes that I made (above), and then at least another month to see if I can test the "Curse Pact" option.