I agree, the solution would vary according to the industry. I think a generalized transition planning for solo founder startups with share holders could indeed address this.
As far as solo founder SaaS is considered making the code open-source does reduce the project becoming dead when the founder is incapacitated, We're just starting to see open-source software as viable solo founder business. Even then the revenue is likely through enterprise support which are again limited due to high bus factor and SLA issues ( /problems/153 ).