Okay, so maybe it's just me but the wizarding world has always striken me as a bit backward in the social department, and especially given it's the twenties, I don't imagine anyone noticing that Newt is autistic and not just weird and annoying.
So I want Graves sent on a diplomatic mission to England. Ever the pragmatist, he sees it as a perfect occasion to thank Newt Scamander for his part in his rescue. Before he gets to meet him, though, he hears a lot of comments/heads-ups/jokes/advice about how "strange", "weird", "annoying", "insane", "crazy", "awkward" etc. Newt is. Once they meet it becomes clear that the people have been right but as they pass more time together (maybe Newt is a consultant to the Ministry, maybe he hangs around with his brother until his book gets published), Graves realises there is a pattern to Newt's strangeness. Basically, I want Graves realising that Newt is slightly autistic but not any less a capable adult for that and Newt slowly falling in love with him but having to hope to ever get his feelings reciprocated (of course they are).

Bonus points:
+ homosexuality is very much frowned upon (just like in the muggle world in that time)
+ Newt's family being extremely patronising towards him (they're well-off, respected wizards of high social standing and they treat Newt's passion as a way to get him occupied and not shaming them publicly; or they think him a bit dim-witted)
+ Newt's book getting published only on his brother's insistence
+ self-loathing Newt
+ Graves being actually a lot like GrindenGraves in the film