My previous place had an unofficial no-meetings-on-friday policy, which meant most people worked - productively - from home on Fridays. Tons of flexibility, and it meant we, as a team, kept ahead of the game because everyone used friday to knock out not only the collection of "oh, if only I had time" pieces that collect over the week, but also those "I need 3 hours, uninterrupted, to really dig into this" big-think pieces. No one overly abused it, and the not-infrequent fade out ~4p still meant the week's overall work was more productive than if everyone worked that last, useless hour on Friday.
That being said, we were a globally distributed group, and had already adapted well to well-calendared and well-prepared-for remote interactions over chat, conference calls and video calls.
Yes, you lose out on the hallway-chats, so it becomes important to have some central hub of people, and to make sure that no one sub-team was completely disconnected from the pulse of the office, but it can be done, and done well.