Other than Keith Olsen, the only producer I know of who has produced Lindsey (without Lindsey co-producing) is Jon Brion (three songs on this soundtrack album):
https://www.discogs.com/Various-This...elease/5477711
Brion is a major talent and would be a great collaborator if Lindsey is healthy enough to work but not able to sing. Brion does a lot of instrumental film scoring, so maybe that's a route Lindsey could take if he can't sing.