I this is your first child, then your baby will not need the big child seat for at least a year - will probably just be in one of those travel systems, so will be fine in the back of the Brera.
You'll be surprised at how little 'stuff' you will need to carry around for the first 6 months, at least. You just need some spare nappies and clothes, pram in the boot and you're good to go. It's when they get that little bit older that the 'stuff' starts appearing.
You still don't need a 'family car'/people carrier when you have just one child - they're quite small, you know
However - it very much depends on who will be using it on a day-to-day basis. Will it be you or your wife reaching into the back to strap baby in/get baby out/sort out any problems? If it's you, then you'll be OK - but if it's your wife, then she will curse you every time she does it, because it will be awkward and difficult, and I'm guessing you'd have to love the car to do it
How about a 159? The rear doors will make a world of difference, the boot is fine (I have a 3 year old, and we manage great
), and you still get the driving experience.