What can I build? - new apps from scratch
You don't have to be bound by your existing systems at all. If you have a need for a new application, which looks too ambitious for now, the Genesis low-code platform could make that a realistic proposition in a realistic timeframe.
Perhaps you need to provide a portal for Prime Brokerage. You could provide clients with online visibility of margin, cash and stock positions, along with event notifications, interactive reporting, and a summary dashboard.