On the scalability issues of onboarding millions of LN mobile clients

In a bitcoin-dev mailing list, Christopher Allen, founder of Blockchain Commons, expressed his interest in hosting a collaboration for defining different sets of wallet functionality. He suggested that this could start as being a transparent shim between Bitcoin-core and remote RPC but later inform proposals for the future of the core wallet functionality as it gets refactored. He wished that the full RPC functionality should not be exposed in Bitcoin-core and proposed the idea of a cryptographic capability mechanism such that the remote wallet could only mask the node functions that it needs, and allow escalation for other rarer services it needs with additional authorization. He also said that this capability mechanism feature set should go both ways, from a minimum subset needed for being a watch-only transaction verification tool to things RPC can't do like deleting a wallet and changing bitcoin.conf parameters and rebooting, without requiring full ssh access to the server running the node. The FullyNoded2 multisig wallet on iOS & Mac, which communicates with a personal node over RPC, securing the connection using Tor over a hidden onion service and two-way client authentication using a v3 Tor Authentication key, is an interface between a personal full node and a user. Refactoring in Core wallets are making good progress, according to feedbacks and proposals on future changes with regards to usability would be greatly appreciated.