doctorbadwolf
Heretic of The Seventh Circle
The Blade Lock's problem is quite simple: "It's always better to Eldritch Blast".
Even you if choose this suboptimal option and get you charisma bonus or whatever, on your turn, if you're not engaged in melee combat, it's better to Eldritch Blast! You can get a taunt/mobility bonus/god's blessing or even the numbers of the lottery as a class feature and you'll still Eldritch Blast on your turn!
So if you want to "fix" the Blade Lock (and I'm using quotation marks because I'm not saying it needs to be fixed) you have give him a better attack option than Eldritch Blast.
Sans Invocations, attacking with a rapier is a better melee option than EB, until 5th level. With Invocations, it's about equal, in melee.
Any point about ranged vs melee is irrelevant, bc no one gets to shoot things with their sword. EB just becomes the bladelock's hand crossbow. NBD.
The problem with Blade Pact is that it's Invocations are taxes, and the other pacts' aren't. Blade Pact needs a little more kick right away, and the equivalent of cantrip scaling, or extra attack.
Being able to cast EB as a melee weapon attack would probably work, two, but might require complicated language to not be unbalanced.