Yay more warlock invocations.

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.

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.