Here are two of my favorite takes on the killing Hitler issue.
The thing about using the non-death of Hitler as proof of no time travel is we have no idea how our current timeline is supposed to be different. Maybe Hitler is relatively small potatoes, and we don't know about anyone far, far worse because time travelers have already taken them out. Maybe John F. Kennedy led us to worldwide nuclear holocaust, with a death count in the billions, so...
Sure, we can invent fanciful stuff to explain anything we want. We're talking about time travel, after all - if any of us actually know, I'm sure we'd find better things to do than post on a D&D forum. So we post what we think sounds reasonable to us, and the more invention you have to introduce, the less reasonable it sounds to me. But I agree - anything it possible.