Re: No passive cooling!
A thought on the NUC form-factor.
Intel needs to put more SATA connectors on it, not just one, so that it can be used as the basis of systems that need >1 hard disk. (IMO every system with locally-stored data needs >1 hard disk, for mirroring - at £40 for a HD can you afford not to? ) How much do four SATA connectors cost? Surely on-chip SATA interfaces are (or can be) designed to idle at microwatts if there is no hardware connected to them? There's clearly no great cost to putting six SATA on desktop boards that rarely have more than three of them connected. If there were, they'd leave them out and the minority would buy PCI-X SATA controllers.
You could connect extra disks by extending the NUC upwards with a section that bolts on top of the NUC box and holds the disks. Keeping the original lid and bolting that on top of the extended NUC would be a nice touch.
If the form-factor catches on the price ought to drop as NUC-format boards start being made by ASUS, Gigabyte etc., along with cases for passive cooling, multiple disks, etc. in various different shapes.
Intel set the ATX PSU format and the common desktop motherboard formats ATX, mATX, ITX. OTOH they failed to persuade anyone that BTX PSUs were a good idea. Standard form-factors are a good idea in principle.