If you want it to bleed sand, then your best bet is to use MOSRotatings, the downside being slowness in large numbers, but that is no different to an actor.
They will be able to do everything else you described as well.
As for interest, that is down to the community, of course. Personally I would like to see something like this, especially deployable sandbags.
Wiki on MOSRotatingsFor custom wounds, I'd just take a look around in base.rte/effects/wounds and experiment.
It should be trivial to make a TDExplosive gib into a MOSRotating, for deployable sandbags.
So, in short, use a MOSRotating.
Good luck!