This problem is harder than you one would think naively.
The problem with this: you need to create a new standard, get everybody to agree to it, and get busy scientists who are concentrating on content and not representation to adapt this new standard in their writing, essentially requiring them to change their habits and spend extra time on writing (which many of them hate), for no obvious gain from their point of view.
I am not saying it's not possible, or not worth it, but it is not easy and simple either.
Besides, in HTML one can directly link to the relevant part.
Being able to link directly to the relevant part is irrelevant (pardon my pun!). Such links are machine-readable, not human-readable. Scientific text need visual citations and being able to name the referred part for reading comprehension.
And Harvard-style citations (AKA name-date) exist for a reason; when your read a paper even in interactive format it helps when you can recognize citations to certain papers and not having to click on them or memorize numbers.
Other styles have their own advantages and disadvantages; that's why they all exist and used by this or that journal, and no consensus on a single "right" style was ever reached.