|No such thing as a small change|
The idea of being able to use fragment identifiers is a good one.
Some pages have them but they're not easy to find. For instance, I can link to the section of "What shortcuts can I use for linking to other information?" which explains how to use fragment identifiers with this type of markup: [href://?node_id=43037#general|General-Purpose Linking Shortcuts] (which renders as General-Purpose Linking Shortcuts); however, you need to know that the identifiers exist on that particular page and then you have to find them. I generally use the "Inspect Element" browser tool menu option for this; another (less than optimal) method would be to search the page's source HTML code.
Many other pages don't have such identifiers, so a first step would be to add them.
A TOC would one way to handle this: I can certainly see benefits to doing this. When I've found what I'm looking for in a page, having an indication of the identifier at that point would be better than having to scroll back to the top to see what the TOC links to. I've seen this type of thing done with unobtrusive link text consisting of a single symbol character: § and ¶ seem to be used quite a lot; I've seen others, many with various types of arrow symbols; I don't really have a preference.
I also think the syntax for such links needs to be made more obvious — it's virtually a hidden feature at present. As I'm writing this, I see a link for "What shortcuts can I use for linking to other information?" almost at the bottom of the page. Following that link, I then need to scroll down five screenfuls (on my 27' monitor) to find the information. Searching that page for "fragment" or "identifier" finds no matches; searching for "href:" finds it but, if you knew to search for that, you probably didn't need to (i.e. you already know the syntax).