I didn't try to load water soluble drugs into w/o microemulsion before, due to the difficulty of finding and choosing a low-density oil acting as a continous phase with appropriate physicochemical characteristics and compatible with SAA/COo-SAA system . In turn, it's easy to use water as a continous phase and finidng an appropriate microemulsion system.
I got the same idea, w/o system to enhance the stability performance of the actives. Some results from the o/w study, show microemulsion able to enhanced the stability of the actives; instead of just the solubility and release profile.