That’s a really great idea. At worst, you leave the company with a roadmap of what they need to do and that’s real value. At best, they can just hire you to do it :)
I’ve found that when you present this in a very objective way, companies are even more into it: “I’m going to leave you with a roadmap, not a sales pitch. You can use it to hire me, hire someone else, or do nothing - I’ll support you guys no matter what you do.”
Yes as long as they have a problem they care about and you can show you solved similar issues in the past they will most likely say yes. Also in the software industry people read quite a lot so they love the idea of a carefully drafted document about their challenges and potential solutions written by a professional.
I’ve found that when you present this in a very objective way, companies are even more into it: “I’m going to leave you with a roadmap, not a sales pitch. You can use it to hire me, hire someone else, or do nothing - I’ll support you guys no matter what you do.”