I'm sure they know they need this, but a quad core i7 processor, 16-32GB DDR4 RAM, SSD (256GB minimum, 512-1TB), GTX 970m graphics or higher (probably GTX 980m unless they're going to wait for the probably-much-better GTX 1070m or 1080m,) or the workstation graphics which I don't deal with at all so have no comment on, other than get 4-8GB RAM version
The Origin EON15-X Pro (the professional/non-gaming line from where Nate recommended) has desktop processors. The i7-6700k is the processor that Jeff and Chris have in their gaming desktops, if that tells you anything about how powerful it is.
M.2 SSDs are super small (2 postage stamp sized, and about half the height of your usual SSD,) so those can be super light, but these aren't quite svelte machines. It'll be smaller than Dusty's, though.
**BRENT**