My proposal is introduce a limit time to conect into a game round.
This will aplied in two things. Firstly, a limitation in the moment in the day in which a player can log in a game. Secondly, a limitation in the total time than a player can be log in a specific game, for each day. But for this second limitation, i will make another post.
Necesarily, this will be a settings in the menu of "create game", and it won't be able to change after the game is created. To limited this, it can be a option only for premium round, or another limit, like a maximum of this type of rounds.
It can be interesting show in the settings of "create game" the main country in every meridian UTC or show the best hours to let log in people from Europe, USA, Iberoamérica,...
A round with this limitation let only log in between 19:00-20:00 UTC, and you can command your country only between that hours.
This will prevent than someone be log in the Europe night and change all orders for his armies.
Against, this must let develop strategies to grant a efective orders to yours army for 24 hours.