[jemolian]

@zink, There are a few things that you can consider: 

• Finding more alternative for the Montanov 82, if you are looking into the liquid crystal emulsifiers, you can consider the others from the Montanov series, like Montanov L which i believe they have tested for having the highest TEWL reduction in the series though it would need a co-emulsifier. 
• You can look into moisturizing emollients or emollients that reduces TEWL such as Isononyl Isononanoate, Isostearyl Isostearate, Sensolene (Ethylhexyl Olivate), etc. For the plant oils, you can use a smaller amount of Grape Seed or Safflower or Jojoba Oil or Squalane
• For the humectants, besides from Pentavitin mentioned previous, perhaps you can consider Betaine (Trimethylglycine) for the skin strengthening effect (see brochure from DuPont), Aquaxyl (from Seppic), etc. You can consider using glycols or diols as well. 
• There are also preservative blends that has hydrating effect as well, such as Symdiol 68.