I hope I've understood what you're asking OK...
People often struggle to articulate all the expected benefits of delivering a piece of work, it can help to think of benefits falling into categories. I use:
Sales or marketing people will usually be able to help you get an idea of what additional revenue you can expect to gain.
Will the idea mean you can avoid spending money you currently do e.g. maintaining an old system, reducing headcount etc.
Work that means you don't need to expand to cope with future demand or pay fines due to non-compliance would fit here
An opportunity to reduce the chance or impact (or both) of a future risk occurring. For example, hardening network security reduces the likelihood that someone will gain access.
Using these categories helps to add some structure to conversations about expected benefits and gets your stakeholder thinking about things other than just their key objective.
To prioritise, a simple method is to take your total benefits figure and divide by expected cost. This ratio of benefit to cost can then govern which ideas you do.
For some other ideas about project prioritisation, I highly recommend reading Developing products in half the time which explores using cost of delay as a factor in choosing when to take a product to market.