I took a brief look, and don't see any globals, gamesettings, casino data settings, or new script commands that will effect the max bet level. I have a sneaking suspicion that it might be hard coded, since your chip stack always reflects your bet - they'd have to create a model or image of the stack for each possible bet.
If that's the case, I can think of one somewhat convoluted solution. Create a new High Stakes casino data object for each casino, or maybe just one, with its own special high stakes tables and chips. The chips would exchange for at a higher rate, maybe 10 or 100 bottle caps each instead of 1. In fact you might be able to just adjust the exchange rates so that all casino chips were like that - setting it to 5 caps per chip would mean blackjack bets would be between 5 and 100 caps.
I am pretty sure its not hard coded. There are a couple mods that change both the amounts you can win before banning, and how much you can bet. Right now I use, http://www.newvegasnexus.com/downloads/file.php?id=34733
Only issue is the max bet size is the same for every casino, and the max winnings before banning is very high. I like your idea of just being banned for a limited time. I also am not a fan of having the same betting limits in every casino. Anyhow I hope the mod I linked is in some way helpful!
edit: I also like your idea of higher chip values!