Every feature is in HEAD, behind a flag. Precisely because managing conflicts cannot be automated, relying on branching is unwise. With HEAD based development, you manually solve conflicts exactly once, when submitting to HEAD, then you never have to think about them again.

Local branches for development, a single HEAD for merging code.

No, features are configurable at runtime. This allows A/B testing or slowly rolling out a new feature. Depending on the type of change, you might test it on 1% of users, 1% of servers, etc.