You seem to be trying to eliminate the whole Pole dynasty from English history! John II (Richard III's nephew) and his descendents.
Since John de la Pole was the officially named heir, surely he would inherit the crown if uncle Richard was killed at Bosworth. There really is no way that Henry Tudor could have been made King, there were simply too many people with proper claims to the throne. Henry Tudor had only a tiny drop of Royal blood, I'm not clear on the details but it seems to involve an illegitimacy, female lines, and even an official disinheritance. I can't see how Parliament or the British people would have recognized such a person as King.
It's very unlikely that the Stanleys would have switched sides at Bosworth, remember that Richard held Thomas Stanley's son George hostage because he feared precisely this event. But even if they had, Richard would have still outnumbered the army of Henry Tudor.