This is off the top of my head and with no knowledge of the progress of the work done already on the topic... so please take this with a grain of salt! I would

This is off the top of my head and with no knowledge of the progress of the work done already on the topic... so please take this with a grain of salt! I would be inclined to try to develop a model of the system and see if I could reproduce the measured viscosity and elastic properties from a simulation. From there you can do things like free energy calculations and figure out which ant-phase is the most stable under which conditions. You're right that in reality each ant is much much more complex than a molecule. But since we're scientists we get to approximate (hooray for spherical cows). To build the model you just treat each ant as an elastic ellipsoid with directional bonding properties. You start off by ignoring the legs and ignoring or greatly simplifying the motion of each individual ant. The first hurdle would be to figure out an ant's bonding properties as this is crucial to the stability of the total structure's properties. Play around with that until your simulation starts reproducing reality; add complexity as necessary; iterate and repeat. As far as experimental measurements, I couldn't even guess what to do next without reading some of their publications.