As researchers we are often dealing with different type of contracts and different rules according to the country where we move. This means difficult management of: activity, pension scheme (http://biondiriccardo.it/researching-the-pension/), affiliation, research funding submission, collaborations requests.
Just a simple example: changing institute you may change email and systematically the old email is closed. What if you are the reference author of a paper? How the people could contact you?
I have already written about pension schemes here http://biondiriccardo.it/researching-the-pension/ but the issues of mobile researchers are multiple. For having a project approved you must have an affiliation otherwise no money even though you are an excellent researcher. Is it so necessary having an affiliation today? There are institutes having fewer infrastructures than my home, or better, my home at least has a color printer … EU is not a country, EU does not have homogenous rules. Thus moving from a country to another one, everything changes including the working and living conditions. At the time our activity can mostly be done in any place, you need a computer, an internet connection, a VPN access and that´s it. Of course if you need to work in a Lab it is different, but even in that case most of the work can be done remotely.
The institute should be the safety for the researcher and for the budget not to be lost, but most of the time there is a common interest (researcher and institute) in getting funding which brings both to close the eyes.
Recognizing the freelance status for researchers would solve several problems, an association of freelance researchers could provide an email from the beginning of the career which could be kept forever, could collect pensions according to common rules approved by all the countries, could provide IT services and could be the reference for any issue. Is it a visionary point of view?