I'd like to suggest that no province should be able to send soldier aid to the extend that it would underpop them more than 10%, and that subsequently no province should be able to recieve soldier aid that would overpop their province with more than 10%
This should if anything make nw manipulation harder, as well as prevent that one noob we all probably had who uppon leaving the game released everything and sent it all to your monarch, thinking he did the kd a favour, but overpoping your monarch in the process so elites left him for several hours. It will not however not prevent people in need to recieve aid, and it will also allow overpopulated provinces to send out what they need to send out.