Startups need to be focused and flexible. OKRs can help a lot with the former, but they'll quickly stiffen your team if you start cascading your goals.
You can't just throw OKRs in a spreadsheet and expect your team to be outcome-driven. You need first to get the right culture to create an environment where teams can iterate to reach their goals.
There's a lot that we can learn from software teams to improve the OKRs process.
You need to focus on value rather than deadlines for OKRs to be successful. Adopting a Now, Next, Later format for your roadmaps is a simple way to achieve that.