So for this particular example to plan on selling a medical device in US and then decide in executing phase to sell in Japan, this would be a big scope creep in my opinion. I agree with the comments above, but I also think a major concern would be patent protection. When you want to commercialize a medical device you file a provisional patent then you have a year to make any adjustments including adding data to support your device from a clinical trial, other drawings, etc. After a year your provisional patent will “convert” to a PCT (Patent Cooperation Treaty) application which is also known as the worldwide application. Once you convert your patent to a PCT application then you have up to 2 and half years to decide which countries to file in; U.S., EU, Japan, etc. So you need to make sure if you want to be able to exclude others from selling your product in a country, that you have intellectual property protection and this again should be determined earlier on than the executing phase. So you should now when you covert to PCT which countries you want to file on (which countries you plan to sell your product). This stage of patent protection can become very costly, its a lot more expensive to file in other countries like Japan, China, EU, Australia etc than just a U.S. application. Your patent portfolio could end up costing around $100k if you file in multiple countries in prosecution because you need legal counsel to translate the applications into the other languages and prosecution is a lot of back and forth with countries and counsel on office actions.

Overall its important not only to have a development and commercialization timeline, but in parallel to have a IP timeline and make sure that those are working in parallel.