I see only the problem of no ability to change the OKRs, otherwise the core idea of making a plan is right. Changing the goals should introduce a additional change process, because priorities change with new knowledge. I haven't see that done well yet. Maybe just having 6 weeks cycle OKR [1] instead could work better as in Shape Up?
[1] https://basecamp.com/shapeup/2.2-chapter-08