Just a lil curious about the retainer ventures, both Hunting & the Field Explorations have the option to select the lvl of the venture.

But that leaves out Quick Explorations; which has no lvl requirement and will yield you any drop from the game's loot pool ARR to END.

So my question is, how difficult would it be 1.0 code being 1.0 code to implement a quick exploration by expansion choice (lvls 1-50, 51-60, 61-70, etc.) to FFXIV?

The quick exploration loot pool will only grow with the next expansion and the likelihood of getting one of the rarer items will become non-existent.