In practice, what happens even now is this:

• Developer X has a need / desire to add a major feature or make a key change.
• X proposes it to the community, gets feedback & iterates
• X leads the implementation, doing the majority of the main work but with help for platform portability, bugs they missed, etc
• Over time X is considered the 'owner' of this feature and gets consulted on changes to it out of courtesy and for reference, but broadly the whole team and community hack on it incrementally
• At all times, everyone is working within our established design and coding patterns to ensure consistency, platform compatibility, etc