You can disable the UP1.5 units, buildings, models, sounds and camera settings: https://ee2.eu/help/#disablefeatures
I'm not sure what other features you want to remove? The simple answer is: No, if there's no switch in UP1.5 Settings (or a custom configuration command described in the change log) then you can't disable / remove a feature. You would need to mod the game and do whatever you like with it. UP1.5 Launcher features usually have the custom configuration parameters which are described in the change log.