Use masked Kirigami icons with explicit theme colors for shell controls so the Shift icon theme renders reliably across light and dark surfaces. Replace the status-bar battery helper with theme icon names so battery glyphs also come from org.shift.icons.
Give the app-thumbnail close affordance a symbolic white X on a dark circular backing so it remains visible over previews.
Move from a C++ library + QML plugin to a QML plugin only for simplicity, since the homescreen switching architecture will be done from Plasma, and so use of the shell library only needs to be from QML.