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The idea is to use it for various important account related notifications. For example user would want to know if there was an owner authority change recently, or upcoming governance votes expiration, etc.

If I right understood you it should be such notifications which user can see when he use Hive keychain or other tools. And this tool shows authorization or let's say transferring funds.
Also I think it may be useful to to users to add in Readme section in repo minimal needed configuration to try it in testnet on virtual machine /locally. Or maybe I missed this point there.

Well, it's work in progress, and I don't think we can easily tell the strict minimal requirements for the testnet version (way more demanding because of the underlying backend).
I just ran it on an Intel(R) Atom(TM) CPU N2800 @ 1.86GHz with 2GB of RAM and HDD, and it works. Annoyingly slow, with seconds of delays, close to unusable but still. YMMV, as there are tons of various factors, including BCAK ;-)
Mainnet version however is slow, but usable on a same hardware so it should give you some perspective on the requirements.