Paolo
Unfortunately for you (and many of us in the same boat as yourself, facing the same problem at many sites) the answer is no - it's
not possible to upgrade an existing MA in this way. Of course, if you have used declarative sync rules you have even more of a challenge because of the way the SRs cannot be 'transferred' to a new MA via the FIM web UI. You
can, however, achieve this outcome by exporting and re-importing the sync rules via PowerShell - if you have this problem let me know and I can look at posting some scripts on the FIMTeam community site that I have developed to do this.
Of course this doesn't help with precedence :/ ... however if you introduce your new MA in parallel with your existing one, you will be able to fix precedence in your lab and deploy (via server export/import) to your production environment so at least you
can manage the transition (precedence of each attribute contributed by your new ECMA2 MA are 1 less than the existing ECMA1 attributes).
It would be fantastic if there WAS a way of retaining the connector spaces of these MAs, or transferring them to new ones, but there's no supported way of doing this. Maybe we should ask the FIM PG for such a feature?