The point of NegInfinity's suggestion seems to have been lost. Eldritch Glaive isn't an actual weapon nor does it use a regular weapon attack. The most important aspect of it is simply that it switches your blast from a Ranged Touch Attack to a Melee Touch Attack.
A regular melee attack is AB vs AC. A melee touch attack is AB vs (10 + Dex + Dodge+Deflection+Size mod), so a Melee Touch Attack has quite a bit of advantage over swinging a normal weapon when it comes to a heavily armored target.
Also it would allow Warlocks to build for strength instead of dexterity, which admittedly offers a degree of variability, but I'm having a hard time seeing how that variability isn't already there. Strength Warlocks already seem viable using Hideous Blow.
For what I think simply making it two melee touch attacks per round that apply blast damage would be the way to go. Eldritch Chain does 2x+ normal blast damage on 3 targets or more (against six targets it does 3.5x the damage of a single blast, assuming it hits all six). With a change like this there would be a more decent variance of mechanics between this and other blast types, as the Warlock will have the flexibility to choose between AOE blast damage and higher single-target blast damage.
Also keep in mind that this doesn't mean "Warlocks automatically double up their blast damage." Two melee touch attacks per round means sometimes (in fact quite often given the way the game's RNG table for dice rolls is designed) you're GOING to miss one of those attacks in a round. Even if your touch AB is 99, those 1's come up a lot more often than 1/20 times.
Just my thoughts. If it's not at least as good as Hideous Blow, no one will build towards use of the feat. Warlocks are already quite viable on BGTSCC, though, so something like this seems pretty low priority when we still have outstanding bugs from the big update package left to fix.