Answering your question, there is one way to solve this situation but it will change gameplay DRAMATICLY. First of all, game should have removed time boost option on geoscape (to avaid situation where ground combat lasts for 2 in-game months, for example) because all players must be synchronized in game time. Also, ground combat MUST be played IN REAL TIME with limited combat time, lets say 5 minutes (eventually game could allow active pause but no longer than 2 minutes per whole combat so battle should take max 7 minutes).
It's risky and controversional, I know, but nothing better I can tell you for now about it.