It is quite often described in literature (e.g. see here) that drugs may cause problems due to their low solubility and/or low absorption characteristics through the GI tract. To address such issues, often it is suggested that solubility of drugs may be improved which would increase the absorption, thus would provide better drug and/or product safety/efficacy profiles.
In this regard, it should first be noted that the low solubility of a drug by itself should not be the cause of a concern for efficient absorption, as the body, in particular the GI tract, does not require high solubility of a drug, or complete dissolution of drug at any given time. As explained previously (link) continuous/repetitious process of absorption in the GI tract take cares of the low solubility and/or dissolution aspects of the drugs.
Furthermore, it should be noted that both solubility and absorption are inherent or intrinsic properties of a drug and cannot be changed. It is just like molecular weight, melting/boiling-point, density/specific gravity and spectrum (e.g. UV) of drugs, which are intrinsic properties, and identify a compound or molecule. If any of such characteristics differ or change then that means that compound or molecule is not original and morphed into something different. Therefore, if solubility and/or absorption of a drug are changed, intentionally or unintentionally, then the drug is not the same molecule which body would see. Its absorption and/or pharmacokinetic (including metabolism/elimination) profile may be different as well. In reality, it would be a different or a new drug itself with its own efficacy/safety profile. Therefore, one should be careful in seeking improvements in solubility/absorption profile of a drug which may result in a potential new compound/drug, and may require separate safety/efficacy profile assessment.
On the other hand, if a physical mixture is made with other components, by simple mixing or complexation, which would dissociate within the GI tract, then the drug will behave as the original. Thus, such “new” formulations would not, at least should not, be of any help or use in changing solubility and/or absorption characteristics of the drugs.
