This is a perfect opportunity to use one of Yamaha's excellent "free play" styles. One of the Ethereal styles or Brass Band Hymn might work, if you drop some of the voices out.

I often encounter this problem with traditional liturgical music. I can't tell you how many hymns change from 2/4 to 3/4 partway through. Rhythm / drum / percussion just doesn't sound right- what's needed is a strong bass, and the phrasing is punctuated by periods of silence. Sync stop helps but it's hard to do convincingly.

I really wish other manufacturers offered rubato styles similar to the Yamaha ones I mentioned! -Ted