If I recall correctly, part of the consideration when deciding punishments for PSR breaches (see Everton/Forest) was whether their misdemeanors had led to sporting advantage or not.
Making payments off the books to secure players they otherwise wouldn't have signed sounds like a pretty clear sporting advantage to me!
10pts deduction per charge and stripped of all trophies won during the offending period. Absolutely disgusting that we had to play a Champions League final against a bunch of cheats.