I’m constantly (maybe even too much?) recommending Merkeleon software. I think that’s pretty much what you’re looking for: they have hot & cold wallet insurance, support up to 250 currencies and lots of payment services, built-in trading platform (for tokens, crypto, fiat). They’re not open-sourced, as far as I know, but they offer a lot of customization options. Either way, it’s a great cryptocurrency exchange software.