Transports only through ports!
Quite a few months ago I had seen a mod on the Steam Workshop called "Port Only Transports". The premise was simple, transport fleets can only leave out of Port cities, but can land anywhere. However, for some reason the author decided to take his version off of the workshop. I'm not entirely sure why, but seeing as I enjoyed the mod I have decided to remake it for TWC.
My version of the mod also increases the action point cost of a transport fleet going from sea to land slightly, making it so that once landed an army can move little, if at all. This makes deciding where to land all the more important as you will not be able to retreat if attacked and will have to fight where you stand.
To install, simply unzip the file and drag the now unzipped .pack file into your Steam/Steamapps/Common/Total War: Rome II/Data folder. Check it off in your mod manager of choice and launch the game! It is save game compatible.