GASP! But why would you want to kill your baby, Jane??
tl;dr version: Core UI should just be part of this /core team with a UI component owner. Instead of a separate UI group (that wound up being the core ui/css group), we create a central Design Corps made up of designers (graphic, interaction, web, print, etc) that contribute to all the groups across the wp project, not just core UI.
Proposal has some support over on UI blog in comments.