Quote Originally Posted by Zaydos View Post
My opinion would be just make the disarming and grappling blasts normal invocations, except a high level warlock raising his hands above his head and disarming everyone nearby is just too cool.
Actually that takes care of my concerns nicely. I suppose the image of a Warlock's Eldritch blast turning into needles that pin the enemies clothes to the floor was just stuck in my head

Quote Originally Posted by Zaydos View Post
Also I'd say the Force Blast ability probably doesn't need to have a reduction to damage as Force damage is easier to resist than untyped damage which the blast already does. Even then the blast isn't that useful unless your DM runs a lot of ethereal/incorporeal enemies.
That's an interesting proposition. Though I would then be tempted to add another effect.
Hm, I need to look up force spells.

Any advice on an invocation that gives Warlocks the ability to Swallow Whole?

According to the SRD, unless otherwise stated, you could swallow a creature up to one size smaller than you, and a human warlock's jaws unhinging as he just eats a halfling is a... potent image IMO