The current FMS data structures may be flexible enough to hold the required additional data, however, a specification of what specifically the data looks like is needed.
If you have yet to settle on a scheme, it would be helpful to allow for
mixed time-dependent and static (time-independent) data.
time-dependent data to be sparse/staggered in time (especially if mesh topology it time-dependent; re-meshing is not typically performed every time step, but will occur at some subset of timesteps).
The current FMS data structures may be flexible enough to hold the required additional data, however, a specification of what specifically the data looks like is needed.