How this works is Joker was also a friend of not only Aunt may and Uncle Ben but also Spider!Phantomhive!reader
So how Spider!Phantomhive!reader meets and makes the deal with Sebastain in this is basically reader still temporarily dies in some way, mainly with the court coming after them since in their eyes Spider!Phantomhive!reader has failed them but when they thought they're dead after catching sight of them a few times before they're kidnapped and basically what happens in the original concept.
I haven't found out what the deal would be fully but it's there.
Now HOW Joker gets the kid is basically before Spiderphantomhive!Reader is still with their bio parents something happens to both May and Ben and instead of being handed over to ANYONE else Spider!Phantomhive!reader is handed over to Joker.
Skip to when he gets his kid back.
He knows that there is something up with that butler\assistant is not human, hardly anyone having contact with the main Gotham cast is human and mentally sound as Sebastian is acting.
But as long as he doesn't harm his baby(who is an adult now) he's cool with what's going on.
Now for the Phantomhive family business(Funtom Co) I can see not only Joker making sure no one can get the company but EVERY SINGLE batman rouge is on Joker's side and makes sure not even Batman\Bruce can get it.
The court of owls are alot of things but knows not to piss off the amount of people they did, especially after offing Spider!Phantom!reader.
Now the people at Funtom co actually genuinely care for Spider!Phantomhive!reader and vice versa because who else would actually have full health benifits,paid days off and vacation, a pay check that you have more than enough paycheck you can actually live on and it's not a paycheck-to-paycheck type deal like the funtom co is ranked “#1 worker-friendly corporation”,
Skip to when Spider!Phantomhive!reader returns and takes over it's not really a secret that Spider!Phantomhive!reader has scars or has some other business beyond the company..........BUT with the butler that's always at their side is WAY to terrifying to find out what it is.
I mean sure a lot of the people in the company may harbors a crush on the guy but it's obvious that Spider!Phantomhive!reader comes first and they respect Spider!Phantomhive!reader to act on them.
The last new girl they had that TRIED to act on their feelings\crush on Sebastian asked to be transferred the same day closer to her family which Spider!Phantomhive!reader agreed with since that would lessen the worry on the woman's shoulders with the distance thing.