Steve,

I agree with RCJ in that an insurgency is difficult to define when including the conditions that give rise to an insurgency. Providing predictions of behaviour such as "seeks to postpone resolution of the conflict while it adjusts the power balance in its favor" renders the definition problematic.

These organisational characteristics that are built into your definition are antithetical to your outlook of insurgency as merely a "strategy".

Likewise your assumption of the insurgent as a weak organisation is too restrictive (I agree with Powerpoint Samurai and Bill on this point); it may be that, in a particular conflict/theatre, that actor may employ an insurgency strategy in conditions or relative weakness (not absolute) or through choice.