that’s what i’m saying: imagine you pay 21 sats to someone with an optimised ASIC(?)/GPU set-up, to do the proof-of-work for your note and then you sign it. 

and a PoW provider can be interacted with in many different ways (doesn’t have to be a lightning payment), which doesn’t make us rely on something niche which most new users aren’t get be set up with. 

 What if you could somehow provably burn 21 sats? 

 One spammer with enough sats could also make the lightning method moot? It's just a measure, the solution obviously is as you said "not one thing" .