Sounds promising indeed. The task request also has a 34 STEEM bounty you might find interesting. If you can, as the TR describes " write a proof of concept asyncsteem Python script that does a nonblocking asynchronous signed operation within the context of handling an asynchronous event " before the deadline the 8th of October 0:00 AOE time.

My thoughts are that adding a refund to the microtransaction authentication script ( source code here ) would be a good proof of concept that could reuse a maximum of existing code so that the proof of concept could focus on the specifics of making the two libs play nice.

Within TransferStream::transfer transfer_event["transaction_meta"]["block_meta"] contains block level fields "witness_signature", "block_id", "signing_key", "transaction_merkle_root", "witness" and "previous".

In CookieUtil::process_transfer::process_last_time::process_account, after setting the account cookie mapping would be the place for adding an asynchonous vote using beem transactionbuilder and asyncsteem rpcclient.

But wether you go for the bounty or not, I think that if the bounty/task-request expires without a POC, I shoukd definetely be able to work with what you described. Great work.

Ceterum censeo HF20 esse delendam