This seems the only way to satisfy everyone. There are clearly those who strongly prefer some degree of open office space, and some who strongly prefer private space. However, few of the articles I've read give open+optional private offices as an option.

Currently, some at my company use unused meeting rooms as quiet space but generally prefer an open environment, with headphones on or off. A growing number prefer a casual, social environment like couches and tables rather than desks.

A strong influencing factor is the amount of collaborative work. Those who are working alone on projects tend to be solitary, while those who make many collaborative decisions want to be closer to others. This may reduce the need for formal meetings, which allocate blocks of time for a whole group that may not be necessary or efficient.

Adults are respectful of an open but communicative workspace. Conference rooms are a good idea but folks don't need private offices unless they are a noise hazard to other people.