Hi there mate, it would be great to add
buildable_entities= {"armoured-biter-spawner"}
to all mod units, so they would create bases of their own species when expanding.
This a new feature for 2.1 game

local armoured_original_units = {
"small-armoured-biter",
"medium-armoured-biter",
"big-armoured-biter",
"behemoth-armoured-biter",
"leviathan-armoured-biter",
}
if data.raw["unit-spawner"]["armoured-biter-spawner"] then
for _, unit_name in pairs(armoured_original_units) do
local unit = data.raw.unit[unit_name]
if unit then
unit.buildable_entities = {"armoured-biter-spawner"}
end
end
end

Ah! Good catch! Added that and a few other things. Thank you!

Getting an error on load with the new version, could be some compatibility issues since I have loads of other mods active:

Failed to load mods: Error in assignID: entity with name 'armoured-biter-spawner' does not exist.

At ROOT.unit.small-armoured-biter.buildable_entities[0]

Source: small-armoured-biter (unit).

Thanks for the clean error, that pinpointed it exactly. Bug was in buildable_entities referencing a spawner that only exists when the Snapper nest setting is on. Fixed in 2.0.6, should load fine now either way you have that setting.