[Migen21]

I'm not specifically familiar with the Z4, but looking at it, there is no reason it shouldn't make a great all around bike. Just make sure that it meets your needs. A few things to think about (I'm sure others will have suggestions too).

* Tire clearance. Will the tires you want to use for gravel grinding fit? 32mm? 40mm? Brake clearance wont be an issue, but fork and chainstay clearance might be. Take a close look at this (don't always trust the specs you read online - a different wheel or tire brand can change this spec significantly).

* Towing trailers with carbon bikes can be a bit sketchy. You'll need to consider how it attaches, and make sure the hardware won't damage the carbon frame/seatpost, etc...

* If you are intending to do any cross country or overnight touring, or commuting to work with a laptop, etc... you might want to find something that will accommodate racks and panniers. Otherwise a saddle bag and backpack will have to suffice.

Then there is the standard advice. Make sure it is the right size and you enjoy riding it. Nothing worse than paying a lot of money for a bike that sits in the garage because it's too big/small/long/short/stiff/floppy/ugly, etc...

Don't get too caught up in the bits and pieces. You can always change out drivetrain and cockpit components as needed to suit your needs.