Many recipe for a hot water crust I have seen calls for something like 15%-20% of the flour to be bread flour? Is going AP flour fine, or do I need to do more/something else to make the substitute?
The hot water method is all about making gluten (flour strength) ineffective, so using bread flour has very doubtful merit. A recipe insisting on its use might have other problems (baking too hot or too long, having too high or too uneven thickness (use a rolling pin, period), or using too little fat) that it tries to compensate by using strong flour. Note that fat content is essential - medieval style hot water crusts that used little or no fat were intended as a food preserving shell, not as an edible part of the dish.