If you're adding vitamin e to MP, it really is only for label appeal, not for antioxidant reasons since the oils in mp are already saponified. Honestly, it would be a waste since it will be washed right down the drain & not have very much time on the skin.
As far as adding sugar to MP, there are a lot of MP soapers that say it's fine, but I disagree. I did 2 different experiments with MP & sugar. One experiment I added 2 TBSP to 1 lb of MP base and made my soap with it. I gave a couple bars to some people to test them out. All but 1 ended up growing mold on them.
I also made some sugar scrubs with MP (1/3 sugar, 1/3 MP base, 1/3 oil). Each day I would touch each sugar scrub with a wet hand to get a little bit of water on the scrubs. After about a month, there was visible mold starting to grow.
So if you're going to add sugar to MP base, I suggest adding a broad spectrum preservative. Keep in mind that Vitamin E is an antioxidant, not a preservative.