The ability to save Entities as Variables

Like it says, I think there could be so much use gotten out of the ability to save an Entity as a Variable. It would be an easy way to keep track of entities while also being able to change certain aspects of an entity without having to spawn it first. It could be used in a variety of manners, such as minion summoning that changes in strength, the ability to "capture" certain mobs and safely move them without having to worry about dealing with losing important values stored in the mob, or even just a way to give variety to certain mobs. I don't know how hard this would be to implement, but a system of being able to save the data of an entity to a variable / global variable could be an extremely useful tool for MCreator and would open up a lot of new uses in mods.