"Thank you for the feedback! I'm aware of pruned mode. My proposal adds a mechanism for summarizing historical data and using backup nodes for optional access. This aims to balance scalability with data availability in the long term. Do you see any potential in this approach?"
No,
1. Pruned mode also offers all 5 benefits stated on your proposal, without the complexity.
2. We can rely on Bitcoin node which store whole blockchain data. So there's no need to add new category of node (backup nodes in this case).