Doesn't exist in the 737s i know, but of course we can just overpress the autopilot and it switches to CWS and holds attitude and bank after being released (bank less than 6° gets corrected to wings level). Even possible to just overpress one channel (pitch or bank) and let the other continue on automatics, if you want to switch back from CWS to any other mode you have to activate that mode actively, won't do that on its own. Autothrust can be overpowered by manual input at any time, but it supposedly wears down the clutch if you do it too often.