Euratom projetcs involve scientists to be sent abroad for days, weeks, months or years. Not sure if you can have a Freedom of Movement specific to scientists. It would mean that the worker is able to move but his/her family wouldn’t. Plus, what if you have a career change, then you lose this right?

My personal opinion would be you have a complete Freedom of Movement or you don’t. I struggle to see an “in between” arrangement. But I am not an EU law expert, so it is just me speaking my mind.