It would be great if there was a way to make and flash an image for the Vera Plus that includes a basic Linux and OH2. The Vera Plus has a nice collection of radios and only costs $149 US. Specs:
Would this be in any way possible, and if so, would it be usable?
I don’t have an answer to your question but looking at the connectivity spec piqued my interest in your question.
As I already have a Harmony Hub I was contemplating getting the Harmony Extender to add ZigBee and (another) Z-Wave but maybe this is an alternative.
Possible, maybe, useable, no. 
With the exception of the radios, the CPU/RAM specs are anemic if you’re planning to run (traditional) Java releases directly on it. From the core CPU/RAM specs, it’s lighter weight than a Raspberry Pi 1.
The Linux drivers for some of the chipsets may also be an issue. Last time around they had to get drivers custom written for openWRT in order to handle the specific chipsets used (for the Vera3/VeraLite models).
If you’re hacking it for the radios, you might be better off with simply Bridging it to openHAB, since everything paired with Vera should come across it without issue, and you’ll avoid having to deal with the Unix driver layer, working at the higher abstractions instead.
The ZigBee radio would come in handy, BT is questionable (given range). For those that don’t need the extra Radio’s then, at $99, the VeraEdge is much smaller and makes a good choice…you can place them where you need them (not where your openHAB instance is running)
Overall, these machines are light-weight for (traditional) Java to run on directly.