The other problem with locking as payment is that I think there is still a fundamental behavioral tradeoff that I think locking falls on the wrong side of, precisely because it seems so convenient. One key goal of rent, at least in my opinion, is that contracts that developers and users forget and stop caring about should disappear from the state by default; forgetting about economics, achieving such a state of affairs is by itself enough to get the majority of the gains that we want to achieve from a rent scheme. On the other hand, if the majority of developers continue to by default use a scheme where contracts last forever, then there continues to be a tradeoff between either contracts being very expensive to create to begin with or the state size not really decreasing.
That said, there is a scheme based on pay-to-resurrect that I think could solve a large portion of the UX issues, that I’ll expand on in a separate post.