On the scalability issues of onboarding millions of LN mobile clients

The discussion revolves around the current thinking on light clients and incentivized full node services. The idea of pure broadcast systems like geostationary satellites or radio systems with various trade-offs between range and bandwidth such as amateur radio, unlicensed UHF and community WiFi is presented to support light client users and encourage full node diversity. Additionally, protocol features that support low-bandwidth broadcast and local peer-to-peer networks add resilience to the Bitcoin network because they can not be as easily sybilled, censored, or surveilled en masse, as centralized ISPs can be. Bandwidth is the primary limitation of these alternative last-mile networks compared to nodes using wired internet connections. The author proposes a system that lets light clients access full nodes over local peer-to-peer networks, which could make self-custody more accessible to light-client users and more local full nodes incentivized to provide services over local peer-to-peer networks could help increase the geographic diversity of full nodes. Three scenarios are presented: two nearby light clients can exchange cached block headers, block filters, and full blocks over Bluetooth or shared local WiFi; a light client can query an ISP connected full node on the same unmetered local WiFi network and exchange differences in block headers opportunistically or pay for large missing ranges of headers, filters, or full blocks using a payment channel; and an off-grid validating full node can receive block information from the blocksat but cross-validate block headers from nearby full nodes connected to ISPs and light clients with cached information via low-bandwidth long-range UHF mesh radio. The author also believes a light-client could confirm specific transactions by querying for Merkle proofs instead of full blocks when using a low-bandwidth long distance and/or multi-hop radio link without the same privacy linking concerns these queries would have if made using an internet address tied to their identity or more specific physical location. This could be a service that can monetize and support the operation of a full node.