Non Robot Workers

[Tree Puncher]

Workers that are needed to make various buildings. Low tech buildings need more, automated buildings need less.

Workers are made in a house building and require food from Angel's bio mod. The lowest tier assembly building needs many workers. Higher tier assembly buildings have automation and require fewer workers. Lowest tier gun turret is just a many workers with machine guns. Higher tier turrets require fewer workers as crew to a tank turret. Lowest tier inserters are just workers, etc.

You could have access to start game flying robots in the form of workers. Instead of recharging at roboports they consume food at a station. Power can stand in for food and their ports require food delivery rather than electricity to recharge. Early game personal defence bots could be workers with machine guns.

[bobingabout]

Robot workers (Logistic and construction) were made to fly to keep path finding simple, they literally just head in the direction of the target. This was done so that they didn't need to add a path finding system for them, which would slow the game down.

This is how 10 thousand robots can be in the air at the same time.

[Tree Puncher]

I don't have any problem with flying.

For the early game you could have workers/colonists that could perform the role of starter tier 1 buildings so you don't need magic buildings like automatic ore crushers made from only stone and steampunk gun turrets that don't need electricity.
Workers/colonists could be created like wood is in the greenhouse.

2 colonists + food + water connected = 3 colonists.

Tier 0 mine: 10 colonists + 10 iron plate
Mining power: very low
Mining speed: very low
Consumes food for fuel

Tier 0 inserter: 1 colonists
Items per minute: very low
Consumes food for fuel

Tier 0 Gun Turret: 2 colonists + 1 machine gun

Tier 0 Construction/logistics Robot: 5 colonists + 5 iron plate
Speed: very slow

Tier 0 Roboport: Consumes food as fuel

Another method would be colonist housing that transmits power in a radius like a power pole to represent colonist labor. But I don't know if there can be multiple flavors of electricity used by different buildings.

[mrvn]

You could change the recipes to require a fresh worker and produce a tired worker. The worker houses then would have a recipe for tired worker + food -> fresh worker.

[Tree Puncher]

There was something called Stone Age Mod that did pre robot industries but it seems to be gone. I could imagine a mine with sprites of little characters swinging pickaxes.