The game tracks stats for each player & their harvests & displays number tallies for total kills, percent hit, quantity per trophy type, etc.
Casual players most likely have both lower trophy amounts (less diamonds) & fewer kills for their time invested, while having a larger animal variety (non-repeated animals) compared to grinders.
I propose creating an algorithm to look at these various harvest stats in relation to invested player time & have the RNG chance value for spawning a GO increase over time.
Say the RNG value is 5% of a GO spawning. If after 100 hours of gameplay & hundreds of harvests later (including animals like coyotes, rabbits, pigs, etc) the value increases to a 10% chance of a GO spawning. But the trigger for the GO HAS to be from an appropriate GO animal class. (ie, red deer, fallow deer, etc). This would continue to climb over time & kills until a GO eventually spawns for the player. Once spawned then the process would RESET & start all over again.
It'd be nice if the algorithm could calculate separately for each reserve, but if not, then it would be on the reserve the player is currently on if possible. (ie, Vurhonga won't now, but would if a GO is added there). If not, then the next reserve meeting the conditions would spawn a GO immediately after an appropriate kill. Understand, there's no guarantee you'll know when or where a GO has spawned. Also, if not found, eventually the player could have multiple GOs scattered across their reserves.
This shouldn't affect grinders in any way because they are already mass killing animals on a large basis & in a shorter time which means they'll still be getting their GO trophies at a much higher rate than a casual player. But the process should increase the chance of a casual player getting a GO trophy for themselves a bit quicker.