If we strongly feel that VE is the future of wikipedia and are making it the default editor than we should be consistent at an article or section level.
The thing that I feel is paralysis of choice, we already have enough users that don't understand the concept of editing much less the confidence to go edit. I think that Visual Editor goes a long way to help reduce the fear associated with editing. We will be taking a step back if we make the user decide between two methods of editing, increasing the steps and cognitive barrier to editing.
I've quickly mocked up 3 options based on a conversation we had in the UX group for placement of a single edit action, that would point to the default editor environment for the user. The last one would be better if the left margin on the body copy was a bit wider.
To address the issue of users wanting choice, I would postpone that choice rather than making it a barrier into the edit environment.
A quick sketch of access point for opening the wikitext editor from within the visual editor environment.
By deemphasizing wikitext editor we both send the clear message about our intentions to have VE be the default edit environment.
Again, in this particular instance I think choice, even though requested by some users is antithetical to our overall goals of a seamless experience for getting users, especially new users between read and edit environments.