Don't get me wrong, but I think with right circumstances, <PERSON> can be realistic.
Look, you have vigilante who since he was kid, was driven by vengeance who killed his parents. He is rich, so he have proper resources to get best experts in each field to teach him all what he needs to know to be <PERSON>. As he has a goal and his mission, he will not side track and waste his time on fun with his friends. During the day, he could hide behind mask of eccentric billionaire, who is always sitting as his home, and afraid to come out, and die like his parents. As long as he pays all his bills, nobody will ask many questions.
Real version of <PERSON> would be bit darker than original one, and It will have shorter life span than one from comic books.
So let's fix that. Let's create <PERSON> not as individual, but as team of people. Who do we need to meet given requirements.
1. Multimillionaire who wants to throw some money away on Batman Initiative. He is financial expert, he knows how to make a money, and how to hide them. 494
So BI funds can be untraceable.
2. Two highly train soldiers, It will be best if they got training from special forces SAS, Delta Force etc. One of them is guy who wears the suit. We need two in case of emergency, if one of them got injured, then we can quickly replace him by another one.
3. Operator, highly educated individual. He is the brain, using small cameras and various sensors he sees all what batman sees and even more. Together with his knowledge and analytical skills and internet access, he can solve any mystery and find almost right away where to send <PERSON> to get more baddies.
But, if we can go slightly beyond constrains, BI could be government covered agency, created to deal with very dangerous criminals who can't be dealt in normal circumstances. Because they corrupted local law enforcement, have influences in high places or have extremely good lawyers. If we go with this route, BI team could be slightly bigger, access to some data could be simplified and would be easier to cover some tracks. 824