There are two ways to 'inject loot dynamically': one of them is to just add it to the drop tables, since loot is technically not determined until it's being looted; that determination uses a pseudo-random number generator based off the sector seed value. Which means that the contents of a given ruins set will always be the same if the loot tables remain constant. So, if you enable a mod that adds a droppable blueprint, for example, then your exploration has a chance to find that blueprint, even if the mod that adds it wasn't enabled when the sector was generated.
The other is to use whatever mechanic is used by the flashy person / old person with book bar events; both of those create new items that weren't previously present and add them to the loot from a specific thing.
(Or, if the goal is just more stuff in general, it might be worth grabbing an old copy of Starsector from when one of the skills actually increased rare loot drops, and seeing how that was implemented...)