This looks like a highly interesting thread, which I don’t have time to read thoroughly and with the concentration it deserves right now, unfortunately — but I’d just like to state (apologies if this has been covered) that in the notation software market, apart from the two “big ones”, there’s already at least one contender that’s “biased exclusively towards” so called commercial/contemporary music, with highly developed integration with sequencer/playback environment.
But a lot of its design decisions (across multiple versions) have been at the expense of really high/publishing quality notation output (at which Dorico excels like no other score editor at the moment). I find the philosophy and the groundwork behind Dorico a great foundation to start with and build upon: in the areas which Dorico is already at its “most complete” even as v.1.0.0, no other score editor comes near (especially if you consider “out-of-the-box” settings/WYSIWYG interface/ease of use).