Lots of templates will be required to make this wiki convenient to use and pretty to look at!
Discourse has a pretty powerful native template plugin[1] that might do most of the heavy lifting. Wikipedia uses some special script extensions to do this part.
The Discourse editor handles HTML pretty well—so from there, it’s a matter of writing (or stealing) the HTML for the templates to function properly, and making the CSS look good.
Top 3 templates I can think of that are absolutely required:
Citation needed template
Image formatting template
Infobox template