Location: L'ville, GA
Hi John ... I fully agree that a lot more attention needs to be given to Stops and TradePlan ... *starting* with just making the existing stuff work properly, then moving on from there to adding Reversal capability, other order types (IB has a zillion), and ability for a Script or OLang routine to modify the allocation percentages.
BUT ... as it stands right now ... with a couple of qualifiers ... you can do pretty much what you are talking about re a trade turning south. No, TP's cannot do Reversals (and I'm glad about that, since I'm scared of a TP *accidentally* creating a reversal due to partial fills at the broker). But it *can* readily be set up to "scale out" of a trade, as "warning events" occur.
You described those events as opposite signals from a System ... but they just as well could be OmniScript rules or OLang Stop rules ... or any of the canned stops that OT and it's many plugins offer.
So, while you're waiting for a major overhaul, you might try that out. :~)
And, btw, over at TradeTight I'm about to release a really powerful Trade Management routine that integrates support for multiple and intermixed AddOns (scaling in) and PartXits (scaling out). So, my prior statements are not guesswork ... it can be done and, done properly, it really helps!