Hi Telson - No question is daft mate... often it prompts perceptive people to think outside of the box
'Uncontrolled' and 'push' 'starts' as defined in my original post is designed for, and only works with, (reasonably sure) Ai aircraft and clients generally over-ride any form of late activation as set by the tick box.
It is probably doable by setting specific aircraft / groups to have a later 'start time' than specified 'mission start time' but I have not tried it but may be worth trying as a simple method.
You can also check if the client is alive when they shouldn't be and destroy it by using Switched Condition>Unit Alive and Flag x is false > Do Script Unit.getByName('unitsName'):destroy() or something similar but this is probably too complicated ....