Compact like the A1200 (key and computer in one), component or HDMI connection, proper standardized plug'n'play joystick ports like in the old ones. Make it upgradable, but only to the same degree as the old ones. It should be a competitor to the console market. Maybe have the keyboard detachable, so you can just pick up the keyboard and leave the base. Powerful enough to compete with the console competition. Open platform, to leave room for homebrew and a vast amount of useful apps and utilities. Pre-installed with AmigaOS, giving you the option which elements you want (uncheck stuff like e-mail client or web browser if you want to install a different one), and make customization extremely simple, by having you remove and install elements of the OS quickly. Super-fast bootup, like we're used to. Ctrl-Amiga-Amiga for softreset.
In short, a powerful console with the benefits of the old one plus some new additions.
Basically, a console with the benefits of the old Amigas.