[ugh123]

Do consulting/contracting work for the large company with the stipulation the work stays open source.

I wouldn't recommend you start selling support tiers and you don't need to start selling a "product" here. Just give them a rate you're comfortable with.

[schoen]

Historically, Cygnus Solutions was very successful at this with custom development on the GNU toolchain.

https://en.wikipedia.org/wiki/Cygnus_Solutions

I don't know if there's something specific about compilers that makes this model work especially well. They would get paid to add specific features to the toolchain that customers wanted, and also to help the customers fix bugs or understand how to do what they wanted.