I would fill it with concrete to soak-up half a dozen ATGM, and could carry an acoustic shot detection system turret to localize troops if you want to add up a bit of luxury. ATGM are pricy wonder weapons, very good for ambush and defending from a city. The way to counter is level the front when going forward... it's not pretty against civilians and sturctures if you want to keep the land.
Concrete would weigh it down a lot though. Cage armour would probably be better, and even more suited if you don't need to think about letting soldiers in and out. Sand has excellent thermal properties and could help resist the superheated jet of a HEAT round.
Cage armour & sandbags on top IMO.
Ultimately if it's remotely operated you don't need to be as worried about protecting it like you would a normal tank.
Russians operated rovers on the moon decades ago, they should be able to develop a modern control system for a tank.