Our ideas portal is private, and primarily used by customer-facing stakeholders including sales and support. Since an idea does include a vote because it in itself is an idea and therefore has to be requested or "voted" on by someone or some org in order to be submitted.... it seems that it would be logical to allow organization inclusion upon submission.
Our current workaround with this limitation is that we have to ask our stakeholders internally to add another step to their workflow when they are submitting an idea on behalf of a customer which is not ideal.
1) create idea and submit it
2) go back into idea and add proxy vote, add organization
Overwhelmingly our ideas are submitted on behalf of our customers, so this is more common than not for us.