I don't think that Canonical necessarily needs to design the perfect developer laptop (hardware is hard, expensive and time consuming) rather they could do a deal with one of the current top tier non-apple manufacturers (Dell, Thinkpads or maybe Asus) and then provide complete support for that machine with a complete focus on the out the box polish.

I'm running Xubuntu on an old(ish) Vostro 3750 and with the exception of it's somewhat mediocre touchpad (Alps sucks) literally everything works exactly as you'd expect but that wasn't the case when this was a new machine (certain bits where flaky but got fixed over the following year), if they could provide the experience I have now on a 3 year old machine on a brand new machine with top of the line hardware then they'd be onto a bit of a winner, it would certainly top any list I'd look at for a while since my primary requirement for any hardware is does this work properly on Linux already.