Was Stedman inevitable That's an interesting question. With many inventions you can answer the question by finding the same thing invented elsewhere, by other people. That won't work with Stedman because the ringing community is small and closed, so it seems unlikely that a ringer and band capable of compiling and inventing such a method would already know about Stedman, so could not re-invent it..
More generally we could think about the likelihood of a method like Stedman being invented. If 'like' means a principle then there aren't many - a tiny handfull out of tens of thousands - and they are little more than curiousities. In the last 20 years BB has ~17.5k performances of Stedman, very distantly followed by ~800 Erin, ~50 Shipway and ~25 Duffield. Shipway is the closest in concept to Stedman, and given the dominance of 8-bell ringing one might expect it to be far more popular. But it isn't.
So Stedman must have a USP, the most obvious being that it got there first, and that probably makes the original question unaswerable.