The Hermes is supposedly unified in design with the SA-22 (Pantsir-SM) so having a large battery of Hermes missiles on an Armata chassis makes sense in that it can hit point ground targets and aerial targets.
Its basic design has a long slender low drag missile on a solid rocket booster... the solid rocket boosters and standardised and come in a range of sizes and powers... and I would suspect a lofted trajectory would greatly increase effective range against both ground and air targets.
A sustainer motor could easily be fitted to extend range and maintain a high flight speed... it could be a ramjet or scramjet to ensure high terminal speed.
For relatively close air and ground targets I would suspect command guidance would be the best option for low costs, but MMW and IIR guided models would be useful against both air and ground targets in a fire and forget mode.
What kind of velocities can we expect to see in the 57mm gun?
I would think 1,100m/s for full calibre high velocity rounds, and perhaps 1,600m/s for APFSDS rounds, with standard rounds travelling at maybe 900m/s or so.
The very rear mounted turret of the T-15 is because it does not penetrate the hull... with a 57mm gun it would need to be mounted much further forward like the 125mm gun turret of the T-14.