I for one am a huge fan of TypeScript, and am intrigued by the idea for R. R definitely feels like a significantly different animal to me than JavaScript, but I don't know enough about the underlying architecture to really comment on the feasibility. I will be curious to see what others' thoughts are.
A related idea that might fit the bill for the present is Hadley's strict package: designed to make R a little stricter and deal with some related problems up front.