You could always just have strings on the LH and pad up the middle with that, or even PLAY a string part as an audio overdub in Cubase (probably the best way to get the voicings right).

But all you are really looking for is a color to add to spice up the middle, and give you somewhere to build and ebb to and from. Doesn't have to be strings... a mellow string synth pad or other pad will do just as effectively. Essentially, you are looking to break up the 'sameness' through the song. Even a fill and a busier Variation for the middle chorus (maybe the guitar picks just a bit busier or another guitar joins in) will do the trick...

And yes, the FC-7 is my secret weapon! I could not play without one.