I'm not sure why the models supporting radiators should be open-air; if you can only fit one CPU and one GPU, then you don't really need a 240mm single radiator, you should be able to fit two 120mm ones instead, at which point you shouldn't need much air cooling for other components at all.
The smallest case is pretty neat though, but it's expensive to begin with, and you'll need to spend extra to get components that look good together, plus any extras you squeeze in like lighting and such. Also you'll probably want to only do this if you're someone with a heap of spare cables, otherwise you'll be building the system part-way then ordering a bunch of replacement cables for anything that can't be routed neatly.
That said, I do think a well design internal layout can look great, but yeah, you'll have to pay quite the premium to really make the most of it.