I agree with what you're saying here. To add to it though I consider paid relays to be a streamlined version of PoW.

In the nostr PoW scenario, a normal computer or phone would not have enough power to quickly solve for a note with high PoW, there would be providers of PoW services which you would have to pay for them to solve your note. Same with Bitcoin, when you aquire it, you're essentially paying for the miners to solve the PoW for you since your own computer does not have the hash power.

So I think that in nostr, simply paying for a relay with lightning, *is PoW. (because it's Bitcoin) and it cuts the complexity down because you don't have to build specialized alternate PoW services. So the only reason you would want the nostr only style PoW would be if you didn't want to use Bitcoin/lightning.

Although one additional upside of a PoW nostr standard catching on would be that you could post to more relays, as your PoW service would be like a pass to multiple 'paid'(PoW) relays. Which is also something I think would be cool for paid relays to do is that when you pay for one, you can post to more than just one..

So yeah, we got options! 🚀