There's no problem using the HWBOT database for hosting own competitions or using the HWBOT rules as guidelines for your competition, but you can't expect us to moderate your competition. One of the reasons why we've invested in a competition engine is that it's much easier to moderate this kind of competition: we have a shortened list of submissions, so we can check them all manually and remove those that violate the rules of the competition.
If you're not planning on using the competition engine, there's obviously no problem using the HWBOT database or rules. You will have to check the submissions for the competition yourself to check if they are valid or not. With 400/500 results incoming a day, we can't check each.
For the competitions we hosted so far, we've opted twice to not allow engineering samples. This doesn't mean that it'll be a rule in the next competitions, but it certainly makes things more fair. For your competition, you can choose: ES or not.