Updated to 1.3.0 (see top of this thread) Extended editing capability Analyze tab lists also treasures and relics if any Re-arranged section on the analyze and edit tabs fo rimproved readability.

Sure, but I just find it funny and it never made sense that you can earn loot in a battle in which no one survives to bring home anything.

Yes, which is why I have told you to at least look at the mod  wether it be download and the structure tree, or just on github its self.

Do you also have triarii units? I guess that could be useful not to just lose spearmen.

The game does have "ruins" in many scenarios, which provide stone. The problem would be to take care of a more seamless transition between all kinds of buildings and their corresponding ruins. Maybe later on all these concepts could be unified in a coherent framework, but right now unbuilding/unproducing seems the simplest way.   The game already includes Loot from killed units. Realistically, to the victor should belong the spoils, but as you say, in a game like this it's hard to determine when a battle ends, thus individual opportunism is what's accounted for.