Hi everyone,
The LaTeX extension v1.13 fixes a few bugs and adds the ability to customize some templates (XDOM and Preamble templates precisely), without having to override them. See https://extensions.xwiki.org/xwiki/bin/view/Extension/LaTeX/Syntax%201.0/#HUIExtensionPoints
See full release notes at https://extensions.xwiki.org/xwiki/bin/view/Extension/LaTeX/#H1.13
Enjoy.