You can interpolate the strokes in the paint node, but:
-you must do it stroke by stroke (letter by letter, all leters drawn with only 1-stroke)
-you won't really be able to edit how it's gonna blend from stokeA_shape1 to strokeA_shape2. No Beziers, no rational points: you can only consider the beginning and end of the stroke, Shake will do what it wants with all the points in between.
After Effects is the real thing for whatever you want to do with text, beyond LiveType. The animation presets from 6.5 onwards are the cheapest but coolest trick around.