This is a great idea and easy to understand abstraction from the deprecated follow list. A caveat though is that it externalizes to relay configuration. Additional features can be built for that for import/export for backups. Im curious of the extent of net reduction in network data consumed through this approach.

It should also pair nicely with any topical lists you've defined. Ive recently sorted everyone I was following into respective topical lists and dropped some in the process. Smaller lists makes for less data being sent to relays for requesting notes then a typical follow list. 

Its about curation in layers. Being in control of your own feed takes effort, but is rewarding.

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