Nosturix sounds nice. 

 1. 
I prefer subscription, especially if I can pay for a good amount of time in advance so I can just pay at once and not have to worry about further charges from my account for a while. 

 Wouldn't random domains get significantly more expensive and easier to block? 

 I'm not sure, maybe.
For the Ditto model it might be perfect to give those administrating their site the choice. Ditto's use case is about using Nostr to grow a community, so might be perfect there. 

For everyone else it still sounds pretty good though. Especially if you can choose which domains to block. Though I don't really understand PoW and and spam mitigation. I need to look that up. 

 Just wait for Corky, the Coracle mascot.