Future steambox should have a modular core for future upgrades
The cooling should be provided by one of those dust resistant sandia coolers
The core should be upgradable. The CPU/GPU/MEMORY/etc should be a sort of push into place/pull out of place design that can be swapped out at a later date for cheaper upgrades of the core. This would prevent hardware stagnation that consoles are crippled with. The upgrade cycle should not be too extreme, say a new core released every 4 years (as opposed to the current and INSANE 8). Ideally games should be designed to run on the past two core generations (that's up to 8 years of compatibility) with newer graphics capabilities available to people with a more modern core.
All the I/O and storage should be built into the console, same with the cooling. The only part that needs to be swappable is the core of the system. External storage is fine of course.
Last possibility, the Core should be something that is manufactured and sold by anyone. AMD/INTEL/ASUS/etc
This will allow a minimum spec to be established and competitive pricing, but allow the pc gaming propensity for greater performance as an option for those who want to spend more.