Oooh, great idea! Let's do it
But, yeah, in hindsight, that suggestion is indeed a little too bloated. I'm still 100% in favor of a dedicated economic unit, simply called "labourer", or whatever. The lack of something that approaches a real economy and and real civilians is sorely missed by a lot of casual players and leaves competitive games with only one real strategy to win: spam the most efficient unit(s) as quickly as possible.
There is a logical flaw in that reasoning, in the sense that a lot of casual players (who constitute the majority) want a more in depth economy. A lot of people think town building and economy management are super fun, and consider the military aspect only as the cherry on the cake. In single player, I often play to build the most beautiful, and realistic looking town, and only start wrecking the AI once I'm satisfied with my little kingdom. But without an economy and the associated hustle and bustle of a town, the game looks a little sterile for casual players, who want to see activity in their towns. We'd even like beautifications like statues, shrines, more unique monuments, even the ability to plant gardens etc... Doesn't even need to be functional. But having the option would greatly enhance the visual pleasure in SP, and enhance immersion. Granted, Delende Est goes a long way towards this, and does offer more replayability for SP, we'd just like to see some of that in vanilla as well (cult statues, villagers and slaves, mercenary camps, farmlands etc.). I understand that's not for everyone, but I'd like to see a little more compromise to facilitate SP. At least DE puts to use those amazing new stables, siege workshops, elephant stables and archery ranges, which would be super appreciated by single players in vanilla (diversifying the look of their towns), but would also please a lot of multiplayers (more interesting strategic choices to make). I'm not saying that the vanilla version of the game should become some sort of economy management game like Banished, but we could have a semblance of an economy, even if it's only visual stuff, like animated buildings, merchants selling wares in the market stalls, blacksmiths hammering at the anvil anytime you research a new tech, some scrawny hunched over NPC slave units scurrying back and forth with supplies and materials, children playing in front of their houses, stuff that doesn't actually affect gameplay but makes the towns look alive, even when your whole army is on the march somewhere.
So, I'm not actually opposed to this if it means the towns will look more alive. It just shouldn't be dumbed down to the point of pointlessness. In this scenario building diversity and placement should become even more important, especially with regard to building farms only on suitable soils, logging camps being built in a forest, with their income determined by the number of trees in it's radius, mines and quarries, maybe even fishing huts, and maybe even storage yards to emulate a virtual resource cap (just like you have to build houses to increase your pop cap), with animated NPC suppliers going back and forth between the storage yards and resource and construction sites, just for the visual kick. Just brainstorming here, but it would make the game a lot more visually interesting/engaging, while at the same time eliminating the micro of economic units. It think it would make 0AD a more mature game, less constrained by the AoE legacy.