Ah, thanks for the clarification.
(Except that the brushes will no longer be accessible in the toolbar).
Just to clarify, the toolbar is located in the header? Or the toolbar is what you would refer to as the toolshelf? If not accessible from the toolshelf… that would be a big issue.
So in essence, the tool brush presets will no-longer be accessible from the top left dropdown grid menu located in the header? If this is so, I still think this is an odd inconvenient idea (alternative UX: go to the Property Shelf on the other side of the screen in the 3D View or to another disconnect editor to change a brush setting, be it the asset browser or the properties editor, also somewhat inconvenient). This means a UX of crossing the mouse accros the entire screen to change a preset, really slow for toggling often all day every day, OR for a UX where calling exclusive hidden floating menus from hotkey is normal - which is not a discoverable workflow per GUI standards.
Will the tool presets be accessible alternatively from a dropdown or floating menu directly from the brush tool button instead? (press and hold the brush, the stored presets scroll out to select?)
… I feel some visuals may be needed on the proposal.