I’ve followed Gasperini since his days at Genoa and have watched his system evolve. In those days (and during his short stint at Inter) he used a 3-4-3 with wingers. There are some full matches posted on Youtube if you want to see how those teams played. Even then his teams played a very strict man-marking system, and it was very difficult for me to figure out their shape. I was never able to put it into practice on FM, but hopefully those with 24 can make it work. I’m stuck with 21 because of my ancient computer.
To understand Gasperini, one must resolve that he doesn’t view defensive structure conventionally, nor does he worry about the ball. To him, the key is for each player to eliminate the threat of a specific player. In doing so, Gasperini’s teams will change shapes repeatedly not only between matches, but within them. While at Genoa he even went into a lopsided 4-4-2 a couple of times and if you watch the Marseille match, they spent much of the 2nd half in a 4-3-1-2. Atalanta’s attacks begin with defense and Gasperini’s teams have become steadily more direct and counterattacking over the years.
Aside from Scamacca the front 3 is largely interchangeable. Their positioning, such that it is, is based upon marking assignments. Only a great coach can put these ideas into practice and not have a jumbled mess.
I suspect that to make this work in FM you’ll need to be spending a LOT of time setting individual player and opposition instructions. You can bin most of the team instructions because they change constantly. For example, there are times when Atalanta play out of defense and there are times when he has the keeper kick long. He never wants to give the ball away cheaply. Mentality of would positive mostly, but sometimes balanced.
One final point that has gone unnoticed is that Atalanta is a very big, physically dominant team. To me they look like a squad that Tony Pulis would love. While they’re not slow, other than Lookman they don’t have any really fast guys either and he’s really more quick than fast.
Here are some links that I think will help. Hopefully it’s OK to post them.
https://breakingthelines.com/historical/the-making-of-gian-piero-gasperini-the-genoa-years/
https://breakingthelines.com/tactical-analysis/tactical-analysis-gian-piero-gasperinis-atalanta/
https://betweentheposts.net/atalanta-bergamo-bayer-leverkusen-the-goddess-engulfs-xabis-immortals-to-european-glory-3-0/
Gomez's small stature made it difficult for him to press larger forwards in the way that Gasperini desires and as the little fella's pace diminished he was allowed to leave. Great player in his day though.