Forced Labour
In v6.40 there is a new type of ground unit - the Forced Labour Unit (FLU). This functions as a Construction Brigade (CB) but with the following differences:
1) It only costs 40 BP, rather than 150 BP
2) It is four times as large, equal to 20 battalions
3) The defence strength is 10% of normal ground combat strength, compared to 50% for a CB
4) It can only be built at populations that have an occupation requirement (currently Conquered, Occupied and Subjugated)
5) 10,000 population is consumed
6) Building one of these units raises unrest by 2%
7) FLU do not count toward occupation strength and do not reduce unrest. Their defence strength (equal to 1/10th of a Garrison Unit) is used in ground combat defence only.
The unit is ideal for expanding construction capacity on conquered planets as (like CBs) it does not suffer due to production or unrest modifiers. While it can be moved to other worlds (or the dilithium mines on Rura Penthe), the transport requirement is considerable. Of course, there is also the consideration of whether your Empire is one that would create forced labour camps.