4 sims games and still no bank or banking system?

I like the premise of your idea but I think you're over thinking it a bit. Businesses are a must. Loans would be awesome. Sims mortgaging houses could add interesting gameplay. Stock market career could be kinda cool.

I would like a bank. I would like to get interest on my sims account. It might actually be nice if rarely (like every 20-30 sim weeks) a recession hit. Helping sims work out how to save money would be a welcome challenge.

But sims have no need for credit and debit cards. This is too realistic forr the sims that needs to have some interactions implied rather than shown to maintain its quirkiness. Atms could be decor in banks but sims don't need them. Unless they simply have a pay-in function to ensure you get your interest.

However, none of this matters without real business so lets hope that is done right first. :D