I have multiple scenarios where folks will be creating ideas on behalf of others. Most prominent are the support team and product owners. Since our portals are only accessible by our employees I have no concerns about exposing the Creator field on the idea submission form.
Thank you for the idea. Currently we allow this via integration with support ticketing systems. You can find more about the integrations available here. If you are not using a system that is already integrated, one potential work around would be to create a custom field which could be exposed on the idea form to capture the customer name.
Given the options mentioned above and current priorities, we are unlikely to implement this idea at this time. We hope you understand.