How do I work around the fact that big companies, that want my service, have policies not do business with small companies like mine?

I'm about to close a deal with a multimillion company for a software solution which will cut cost and make their operation safer. The company entity I'm dealing with wants us and know that my company is the right choice for this particular service. Also worth mentioning is that my company will own the software and sell it as a complete "product/service" to my client once the software is completed. But they said they can't sign a deal with such a small company. So what I think I need to do is to "team up" with a bigger company and let them have a contract with my client for "distributing" my software solution. ( big company is basically doing nothing.) I know this software will help a whole business branch and have ambitions to sell the same product worldwide and keep developing it. But I'm afraid that I will not be able to build and sell this software product/service on my own terms (I.e not move fast and crush expectations) if I'm playing my cards the wrong at this moment. Any thoughts, experiences or ideas? This can be a big leap for my tiny company and I so badly want to get a foot in the door! Thanks for reading!