There is no rule against this. In fact, your 2nd band could also play the same song, since there's no difference in the performance requirements. A SNV only gets extra time in sight reading.

I've seen programs that rehearse their SNV1 and SNV2 bands together, then split them for contest.

If you want to get REALLY fun, you could program a multi-movement work like the Holst Suite for your Varsity band, then EVERY band can play the SAME music. Your NV and SNV bands can just play smaller portions, as they're on the PML with reduced movements.