Upgrade the original radio?

I think it is not a good idea, the marelli integrated system is a strategic part of the network aboard with many controls and diag into it.
If you are not absolutely sure of compatibility with all the protocols and so on you can have big problems.
last but not least you lose the warranty

It won't simply be a plug-and play system, so god knows how complicated the wiring will be and how compatible the car's computer is with the Seicane one. Best not to mess with it and it may void your factory warranty.