"Non-voluntarily"... Someone pointing a gun at your head?
Sorry, ESL moment.
I'm just pretty sure that there are people out there willing to spend credits (a lot of them) instead of sourcing and hauling commodities required for colonisation.
If it wouldn't be for FCs not working rn, half of the job could be done by simply offering highly competitive buy orders for required commodities. The other half could by paid with carrier transfers.
The problems lay in organisation - there are several places where carrier owners can announce their offers, and all of these are more suitable single-commodity trading, not many materials at smaller quantities like we need now. And carrier transfers require additional organisational effort and trust.
An organised community like that could be a very attractive option for both players with credits who want their bases build, and truckers willing to haul for a good buck.