FYI, you can interrupt moves now by revealing in between the steps of a move action. But your arguments against revealing during a step are confusing. Before, my interpretation was that you can not interrupt a phase except after an activation or step because they are explicitly mentioned. But now you say we are also allowed after an "event." If we are, then shouldn't we always be allowed to after an event? And steps may contain multiple events just as easily as phases may. It is logically consistent that if you can interrupt one thing because it contains sub-opportunities for revealing, that you can interrupt other things that also contain those opportunities, and there is no rule that contradicts this. Then following that path of thought and the fact that we don't have a hard definition of event, we end up with the weird abuses mentioned.
Your suggested definition of an event as the combination of initiating and resolving an effect is not a bad one, but still leaves a lot of things open. Such as, I would argue that nothing is initiated during the upkeep phase. You merely resolve effects already in place. Also, this definition does not solve interrupting steps or effects that contain multiple effects within themselves. If you initiate something that involves doing multiple things, such as applying both damage and various effects during combat, can you reveal between these multiple effects or do you have to wait until the entire initiated event is complete? If it's the latter, then wouldn't that apply to initiating the upkeep phase and resolving all of its constituent effects as well?