Having a New TechTree Requirement Per Unit of Same Unit Type?

Is it possible to change the techtree requirement of a certain unit type per each one of the same unit type that is created?

so like i might make a footman that required a castle.. but the next time i make a footman he may require a fortress.. and the next might require an upgrade??

You can add all conditions and remove/add an hidden unit/upgrade... like you want
It is the easiest way and i dont know an other one

Edit : You can't remove an upgrade

Create multiple of the same unit in the Object editor with different techtree requirements (have the reqirements from the previous ones in each new one) and add/remove the different ones from buildings (to change what footman is being made).

That's the only way I see it.