Hi there! I would like to second this motion. I tried to integrate MathJAx by inserting this code into the HTML code of the blog main page.
And then writing a new post using the $$ to delimit the equiations.
It didn’t work. 
Please WiX team!!! We need a way to integrate LaTeX in our blog’s posts.
Could you provide us with an alternate solution?
PS. It does works perfectly in Blogger’s post’s. Please make it work in Wix new blog too.