The most important thing is the whole team being in the same time zone. Even a 1 hour difference is too much. That may seem extreme, but I've had so many important discussions happen around 5pm near end of day when everyone's done with their main task and meetings and have time to think about something else. Then they realize it's really important and need to chat right now. If the team is not in the same time zone,…
And when you mention just one hour timezone difference is a problem, I really do wonder how you deal with flexible work times, or you just expect 9-13, one hour break, 14-18 for everyone? Myself, and many others I know would refuse to work like that (I don't do lunch breaks as I don't have lunch, I prefer to get in late and work late as my brain is mush before 10am, Others that work with me seem to like to start as 7am and leave early)
You seem to want work from home developers to work like part makers in a factory.