Jolly good. Dual FMS is standard for SAR machines, optional for crew change. Our Australian machines have dual FMS - that was required by CASA for GNSS approaches at an IFR alternate without any land-based navaids.
So do your helicopters have dual FMS installed out of the goodness of your heart, or to meet an operational requirement (ie no choice)?
With dual FMS no probs departing with one inop provided it is not required for the above, nor configured to do the radio tuning - although in the latter case it is allowable if configured to do the radio tuning but you have the emergency radio tuning head.