I can't begin to imagine if City is doing a second employer type thing with players, scouts, staff, etc. I presume to be proven is tax record sampling but that's assuming 1) sampling finds person(s) are claiming possible secondary/additional wages, and 2) how the additional payment/wages are recorded in Abu Dhabi if earned there*. Like per say City Group pays player X 10 million for football services but a further 5 million in July when the player reports to X location in Abu Dhabi for whatever reason, let's say a football clinic, and paid for by let's say the Abu Dhabi Sports Authority (or whatever). There's an easy circumvention around FFP, assuming it cannot be stopped. It would not need to be in a contract that I'm aware of, it could be considered an endorsement, or a separate payment for services rendered, verbally agreed between agent and player and a third party, and it would not be paid by City FC despite it all being the same fecking parent shell. It could also be hidden but that opens a player (and club) to severe punishment if not reporting wages. I'd be curious if Mancini reported the additional income in his returns. And I would expect the PL discovery team looking into such.
Herein becomes the issue of a STATE paying persons that would never occur if not employed by a club the STATE owns, and probably why clubs like Real don't openly court City players - they're blown away by requested compensation. Granted, Joe Schmo owner of Club Z could also do the same but much more difficult to negotiate a third party endorsement and especially for publicly reported companies, let alone a STATE organization. The Glazers can't offer a player a services rendered payment in the offseason from the federal/state government, nor can it guarantee a potential endorsement with let's say the Hard Rock Casino in Florida. Abu Dhabi and Saudi could theoretically do this, it's really up to the player to claim on his tax return(s) as far I understand taxes. If legal and/or tax expert is lurking about please chime in, I could be way off.
*US tax returns have a section to report income received outside the US and I presume so do other nations. And perhaps Abu Dhabi can pay the person X wages when in country, which may be easier to avoid various rules in England for this scenario.