The point of a decentralized exchanges is that no one except you has control over your funds. That means that anything you do on the dex needs to be cryptographically signed with thr priv key of your account. That is exactly what the exchange.py module does. Anything else would just kill the purpose of a decentralized exchange ...
Yes, you know that and I know that. Bot operators trading on Poloniex aren't as ideologically driven. Profit is profit.
Btw..
The exchange.py module does not require you to run your own witness node. Openledger's node works fine aswell
a program could be written that PROVIDES a local api that mimics poloniex and deals with signing etc locally if thats what you want
Personally, I don't know enough about the inner workings of Bitshares or Poloniex software to have a good opinion on the best approach to produce a solution to what I describe (a websocket interface which mimics Poloniex WS API).
What I believe is most important is to offer the absolute easiest path for Polo bots to trade on BAE. If the default mode is to bridge through a "trusted" node operator, then so be it. For those who choose to run their own copy for decentralization, even better.
Now, the next question is whether or not there is a capable developer who believes the idea has merit and can deliver.