You'll find plenty of people theorycrafting on these forums already.

Sadly there isn't a compendium (that I know of) to browse all of the suggestions and topics.

The disappointing thing about theorycrafting in FFXIV is that; limited gear, limited stat allocation, limited party compositions.

"INT vs. MND SCH"
"Max Crit SCH"
"Spell Speed SCH"

Are all topics I've seen run through here!
http://xivdb.com/
^If you're interested in finding out max numbers for gear and sets. Other than that... It's just disappointing.