Dynamic self-assembled structures found in complex fluids containing surfactant, water, and oil range from spherical and cylindrical aggregates to bicontinuous microemulsions and ordered liquid crystalline phases. These structures are extensively used as templates for the synthesis of nanomaterials. However, the topology of the initial structures and in particular their characteristic length scales often undergo significant changes during polymerization. Increasing the microemulsion viscosity should slow down its reorganization kinetics and, therewith, help to maintain the microemulsion nanostructure during the polymerization process. In this work, we report on systematic phase behavior studies of a new class of highly viscous microemulsions that comprise of surfactant, polymerizable oil, and concentrated water/(sucrose/trehalose) solutions. It is found that the substitution of H2O by sucrose/trehalose shifts the phase boundaries of nonionic microemulsions to lower temperatures, while the opposite trend holds for ionic microemulsions. Our systematic studies revealed that hydrophilic nonionic alkyl glycosides are the most suitable candidates for the preparation of highly viscous and polymerizable microemulsions.