I'm really late to this discussion. I love the concept for many of the reasons laid out.
However, I will say that I wouldn't trust the current management to do justice to the theme. In order for the concept to work, it would need to focus on universally loved musical classics. But from a business perspective, this would offer far less opportunities for cross-promotion. Chapek can't resist the urge to sell us stuff, so I fear a musical park would be filled not with well-loved music that has passed its peak monetization potential, but rather with whatever flash-in-the-pan act Chapek can promote in exchange for advertising dollars.