Which resource should the consultant recommend to a non-profit organization to suggest new features in...

For suggesting new features in NPSP, the recommended resource is:

Power of Us Hub: This is a community platform specifically for Salesforce.org customers. It includes forums, idea exchanges, and collaboration spaces where nonprofit users can suggest and discuss new features for NPSP.

The Power of Us Hub is the central place for engaging with the Salesforce nonprofit community and influencing future product development.