I'd suggest the weaker team is able to add players rather than the stronger team take them off.
It's unfair to withdraw a footballer from the field and reduce their game time because his team is superior.
Meh it is half an hour every 8-9 weeks. But I can agree with you but that requires a change to the rules. A coach doesn't need to wait for Northern to change the rules to help improve his players by dropping the numbers down by one for 20 minutes.