While I admit Wily's Castle ever being legal is unlikely (to severely understate the case) I would not be opposed in the slightest to a test run for the sake of experimentation. It's largely a question of when does a stage hazard become more pressing than your actual opponent, and different people will have different answers. (I think you already alluded to this, actually.)
You got a few points wrong and I'd like to gently correct them. Also see my thread on the stage
here.
The different transformations are not completely random. You may have noticed that the stage goes through a total of 4 transformations before returning to its start position over the island and doing another 4-transformation cycle. Each one of these transformations pulls from only 2-3 possible locations to stop at. So while it's not possible to completely predict the next transformation, you can always narrow it down considerably.
The main stage only ever gets bigger vertically, depending on which platform setup is attached at the time. (I assume you're talking about the floating platform that carries players around.) The width of this platform is always the same.
The warning sign for departure appears a minimum of 5 seconds before the stage actually moves on. It's not nearly as urgent as you seem to believe.
Walkoff camping (you got the name right) is basically impossible on a transforming stage because not only do you have 15 seconds or less to do it in, it puts you in an extremely disadvantageous position when the stage starts to move on. Very high risk for very low reward.
Last, I disagree with your final statement that it should be banned for further testing. It is very difficult to unban a stage once it's already banned because frankly, most people won't be interested in playing on it even for testing. Then in a tournament where the stage is legal, you have a few people who know how to deal with the stage and a majority who don't and will then blame the stage for any losses, resulting in the stage getting banned again. Instead, the stage should be legal until such time as it has been shown to cause degenerate gameplay.