You are thinking too specific and perhaps PoS was not the best example. But imagine a tiny low-power, low-cost bitcoin node with trivial set-up. I think some people would find innovative uses for these, while others would buy them simply to help support the network.
I'm quite skeptical about this.
You wouldn't mine with an ARM processor. You would mine with a bitcoin miner that employs 1 or more SHA256 ASICs. If the ARM-core bitcoin node was cheap and simple enough, the "hashing device" could be transformed by default into a "plug-and-play P2P miner" by the manufacturer. This may help to decentralize mining.
The reason mining is becoming increasingly centralized is related to equipment costs, power costs and equipment delivery times; mining is simply not profitable on a small scale, and nobody with a little common sense would buy an ASIC miner to run it at home. The availability of a cheap stand-alone Bitcoin node is not going to change this at all.