Brand Themes should present the option for it to be either a local preference or global preference.
When managing a user group larger than 5-10 people (for example having 100+ users all creating content simultaneously), it can be frustrating to constantly check which Brand Theme is currently set as default. Some users are marking the "is default" option, believing it only applies to their personal settings, which leads to confusion. Allowing this to be set locally will mitigate this confusion.
Internally submitted idea