What's "metabolically disadvantaged"? Are you suffering from a medical condition for which no satisfactory diet (in the proper sense of the term) has been developed?

I'm not sure I have all the background information necessary to properly understand all the intricacies of what the OP in the link you posted is describing; but it sounds like what he's going through is complex enough that it probably won't solved by something as straightforward as Soylent (which is basically "let's take everything current science says your body needs, and mash it all together in one solution").

Any light you can shed on this for the non-initiated would be appreciated :)