- Steam+distro of your choice using your preffered DE and steam as software mixes both worlds of gamers and DE users seemingly, but you opt for some performance loss since you run more services beside the fact that your distro might not implement all performance tweaks (target: computer users who want to play and work at same time while not being scared of sacrificing some performance)
- Steam+distro of your choice by using steam as DE like http://www.webupd8.org/2012/12/bette...ance-with.html. still mixes both worlds, but switching requires login/logout. good thing is that you gain some performance as your session is limiting services that would otherwise eat your cycles. even better thing here is that you retain all your services like network shares and such. and even better case is that you're still open to 1st approach since you can run same steam inside your working DE (target: computer users who separate their work and gaming, but want to use same machine for both worlds)
- SteamOS only becomes viable when you don't want DE and computer functions, but want to squeeze every bit of performance and get console like plug-n-play experience (target: console users who only intend to play on that machine)
- 4th one is actually dualbooting your distro and SteamOS which i think you already thought about it your self and don't like it
your suggested chroot approach is nothing but even larger footprint than any of these 4 since you would try running one complete solution on another complete solution. if you want to fit 15 tons in 10 ton truck, you can't to take 5 ton truck, load it, put it in that 10 ton truck and expect you can now still load 10 in it to transport 15 in one go. SteamOS won't solve your usage case, you should opt for one of other 3. but, if your interest only lies in seeing how it looks, install it in virtual machine which will take way less work
that is the beauty of open solutions. if the way it works doesn't suit you, find another way. that is also the main reason why SteamOS should never, ever have DE. all it would do would be take away one of possible usage cases since it would only replicate one that already exists. and i wouldn't say my world is black and white, i just know exactly which shade of gray i want same as you seem to do. i like things separated, you don't.