I work on a remote office, and while I definitely agree that the rapid prototyping stage works better in-person, current tools help a lot - we have a pretty large app that was built 100% remotely (I did ask for in-person meetings but there was no budget).
Honestly, you can collaborate and do almost everything remotely. What does lose a bit is team building, you have to go a bit out of your way to build rapport (but it´s also doable).
I'm still learning how to be more personal while remote. An always-open casual video chat room is a fun idea (especially if you have a screen with it always open in the office!). Games (while on video chat) might also be fun.
Honestly, you can collaborate and do almost everything remotely. What does lose a bit is team building, you have to go a bit out of your way to build rapport (but it´s also doable).