"Each of these project ideas targets a different chokepoint in Bitcoin’s path to everyday, in-person use: usability, volatility, incentives, knowledge, core tech, and integration. A single determined developer can indeed move the needle by focusing on one area and delivering a solution that didn’t exist before (or improving an existing one significantly). The common thread is making Bitcoin/Lightning more accessible and convenient for the non-technical, busy shop owner or the average customer.

In terms of prioritization: an easy POS app (#1) and a Lightning-fiat bridge (#2) rank as top priorities, because they immediately remove major barriers (user experience and currency risk) and can be deployed widely with relatively low friction.