Let me know if I got this right. My understanding is that the Investiture of the Scadrial is there connection to Preservation and/or Ruin which they are born with. So if a Nicrosil Twinborn stored his connection to Preservation (thus weakening his Allomancy while it was being storied) and then burned it, he could increase his connection to Preservation which in turn would increase the strength of his Allomancy. Nicrosil being burned increases the strength of other people's Allomancy at the cost of draining all of the metals that are being burned. So if a Nicroburst is like a supercharger for other Allomancers, then a Nicrosil Twinborn would be like a nuclear power plant for other Allomancers.
