Good idea (also for eventual migration purposes in the future).
Now I use plain text files (.txt- or .md) and put them on my notes. Great, but there is one impractical aspect: Text files are displayed as attachments with no inline preview. I have to use my mouse to click the preview button to get a sneak peak of the contents, which bothers me. (using the Mac version)
Evernote could fix this easily: A simple inline-preview of plain-text files. An added benefit would be rendering support for Markdown-files. Editing happens externally, no problem.