Please note all plugin references from core should use callbacks, it is not ok to use capabilities or links to plugins because they may not be present in customised installs.
There is no need to have whole featured theme selector with previews
etc here. Following the same form element as they have in Mahara, the
theme can now be selected for a given peer at 'Review host details' tab.
I have also noticed that force_theme and theme columns are redundant at
the moment. Keeping them both for future improvements, though.
