Maybe one of the JuMP devs can chime in then, since they know more than me about this, but I’m not sure there is a way to do that. I believe the problem is that deepcopying is not guaranteed to correctly do what you want it to do, because the model is also held by the solver which may be written in another language, and deepcopying won’t extend to copying things on the solver level too.
Maybe you can set it up so you can simply modify constraints within a single model? Constraints · JuMP