Guaranteeing the same text twice might not be so important. There are pixel comparison testing tools for popular browsers. Your advantage is probably speed. Would cypress end-to-end tests run way faster in Browsh than in a graphical browser? If so, you've got something of value to big companies. You might want to partner with or contract for Cypress.

EDIT: Since Browsh depends on Firefox I'm curious whether it's actually faster than a graphical browser.