IMHO, for devs, a modular laptop would be more appropriate: a display panel, a CPU/GPU box, mouse/keyboard, a battery pack... and the bag designed to carry those components.
I think you could make it pretty small but still large enough to fit two small PCI-express cards and replaceable/upgradeable RAM modules. It would be a good format for tinkerers, very amenable to having replaceable parts and being user-serviceable. Throw some GPIO in there and you would have a real winner for the maker crowd.