If you're an occasional cog-swapper, you might want to check out something like
this. Put it on, pedal forward and she's loose. Also travels easily so you can access and change drive side spokes on the go.
Just an idea.
Also, if you're feeling burly, just a section of chain and a FIRM grip (vicegrips?) can keep the freehub from ratcheting while you loosen the locknut.