Does it really matter where WordPress started? I'm more concerned about it's fit for purpose today.
The strength of the loop is it's flexibility. You can use Drupal to get 85% done in almost no time and then spend an outrageous amount of time trying to get the last 15% done because it doesn't give you the control that WordPress does, and the loop is in large part why you get that control. I know, I used Drupal exclusively for 2 years until I switched to exclusive use of WordPress. That's one of the key points of my rant; the loop "feels" like it is less efficient but in practice ends up being a lot more developer time efficient, especially when clients want things to be "just so."
AND if you want to use WordPress without the loop, look at some of the theme frameworks like Hybrid, Thesis, Genesis, et. al.
If you think my project is too complicated it's ironic you mention Drupal. Our approach is much less complicated than Drupal, and it provides more flexibility too, except no admin user interface for create post types and fields like Drupal has for nodes and CCK.
And don't get me started on how much harder it is to deploy a Drupal project vs. a WordPress project. Try deploying a Drupal site with live data already online once, before you stare wistfully in Drupal's direction.
my clients often want to create a page where they can enter content that gets presented in various areas of the page/sidebar/footer etc., but they need to see it all together while editing rather than having a load of custom content types that they have to navigate between
Ironically, that's exactly what we designed Sunrise to enable, albeit not exactly as you currently envision. The idea behind Sunrise is to give pro site builders the ability to give their users a much more straightforward interface for editing what the user sees as a web page. The screenshot I linked above is literally the tiny tip of the iceberg. To show you more I'd really have to do a screencast and I don't have time for that right now.
Even more ironically, Drupal is much worse in forcing users to jump around the admin UI to affect a single functional changes!
And it's not that I "didn't like" what you are calling a "multi-edit" style of plugin, just that I recognize because of the level of complexity of the systems we've built with Sunrise that "multi-edit" pages are only useful in simplistic use-cases, i.e. a 10 page site where the owner wants a mostly blank canvas to write their own HTML. And I also said they would be pretty easy to implement in Sunrise, so how is that "not liking them?"
That said, my guess is that you'll be unlikely to see your requested functionality added to core, at least in the form you propose. I can't speak for certain, but it seems that planets typically must first align before the core team will consider adding any new features into core, especially features that affect the main post edit windows UI as much. Most of the core team would have to agree on a given core UI feature and from what I've seen over the past 3 years, chances of the core team all agreeing on adding "multi-edit" is closer to zero% than it is to 0.000001%.
A key reason we chose to build Sunrise is because the core team typically won't add features that professional site builders need if end-user bloggers don't also need them. So we decided to create a broad and stable extension to WordPress to meet the needs of professional site builder that can't currently be achieved by 17,000+ individual plugins, each doing it's own thing. We wanted to address the needs of ~80% of professional site builders vs. the needs of end-user bloggers which is what ~80% of WordPress users are and who the WordPress core team rightly focuses on.
I'm not really trying to sell you on Sunrise, I merely wanted to offer to you if you were interested. I belabored the point because I felt you dismissed it as "too complicated for your needs" without understanding it at all and I always get frustrated when people dismiss things before they understand them.
But if you are not interested, no worries; maybe I'm wrong and it will be added to core. Or maybe somebody will release a plugin that does exactly what you want and will fully support it so you can do client projects with it. Whatever the case, good luck in finding what you need.