Never take the claptrap that dealers state about diagnostic equipment and the ability to update ECUs to latest spec. Invariably main dealers don't (I've lost count of many cars I've found like this), and EU Block Exemption rules mean that manufacturers HAVE to offer original equipment to independent garages (or anyone who's prepared to buy), which means they can offer exactly the same standards of service.
A really good independant will offer service that is of a far higher standard than a poor main dealer. Sadly, I've yet to find a *truly* conscientious main dealer who really surprises and delights me with their service.
I'm not going to entirely agree with some of your statement here, only because I have personal experience of diagnostic servicing from a franchised service centre. My Cadillac on its first service last year, had software updates applied and my central locking (at my request) was activated to auto lock down on drive off via Cadillac's diagnostic software. In case you're wondering, auto lock down (on suitably equipped vehicles) of central locking on drive off is illegal to activate in some countries (not in the UK though) and is therefore not automatically available on some marques. Also the service I just had on my car in August, the Cadillac service centre I took it to, were outstanding and they kept me informed throughout the two hour service schedule.
I haven't had any experience of Fiat dealer servicing - yet, so I can't comment on their efforts. I have used three extremely good independent garages over the years who I can honestly say, didn't take me for a ride and who appeared to do whatever job I requested with honest professionalism.