For all our efforts to separate content from layout on the web (now generally regarded as best practice), there’s no getting away from the fact that when you write copy you visualise what it should look like when it’s published.
Elements like headings, block quotes and calls to action are all crucial to how messages are conveyed to the reader, so it’s inherently impossible to divorce copy from design. In fact, to resist that relationship between the two is to risk quality at the expense of principle.
So here’s my alternative approach: just go with it
Add that context to your copy when you write, as helpful design notes and direction for a graphic or web designer. Be wary of dictating design of course: “this should be prominent and itemised” is constructive, “this should be emboldened in a numeric list” isn’t. No one likes working with a dictatorial and micromanaging copywriter who treads all over a designer’s creativity.
The net benefit of not fighting the intrinsic link between copy and design is that there’s less ambiguity, so a project is more likely to be successful first time around, as well as quicker and easier for everyone involved.