I'm not judging, mind you...matter of fact I think it's a nifty idea, I'm just not that nervous myself, BUT, if you're going to go through the trouble of having a dedicated device for security reasons, well, I have an AspireOne myself that's been relegated to toy status since traded in my elderly G4 desktop for a shiny new MBP and it runs OpenBSD well enough for your needs. WiFi isn't working but you probably wouldn't want to use that anyway.
And yes I realize there's virtually no difference in security between the two and you can't put STOP on a netbook but as I said, if you're going to have a dedicated device, only 2 security holes in the default install in a heck of a long time!