Re-reading all that - in particular, the various enhancements for affecting multiple sources - I had a thought. The only official power modifiers/sources that can be Neutralized are Magic, Psi, and Super - the only power modifiers that have the -5% for an anti-power. I guess it's surprising to me that a chi-user can't neutralize or disrupt another's chi. And what about denying someone his Spirit powers by trapping the spirit that's providing them? Not an anti-power, but certainly a countermeasure.
There might be more on this list (
http://gurpswiki.wikidot.com/ind:power-modifiers), and of course the GM can create new ones, but +300% Cosmic: All Sources seems like a pretty poor return on those 150 points.