My MSc was on precisely that topic!!
or at a Dropbox link Dropbox - 50351864-Supporting-Narrative-based-medicine-in-GP-systems.pdf - Simplify your life to page 57!!
I thin this would require something like Markdown but with custom markup. CDA had a go at something similar but I think you need go well beyond just embedding Snomed terms to embedding links to all sorts of Structured entries ( e.g prescriptions.