One solution could be to have a document with something like „The 10 most common reasons for rejections“ and send it to people with a disclaimer like „We are wary of giving specific feedback because we worry about [insert reasons]. The reason why I rejected this proposal is well covered among the 10 reasons in this list and it should be fairly clear which ones apply to your proposal, especially if you would go through the list with another person that has read your proposal.“
One solution could be to have a document with something like „The 10 most common reasons for rejections“ and send it to people with a disclaimer like „We are wary of giving specific feedback because we worry about [insert reasons]. The reason why I rejected this proposal is well covered among the 10 reasons in this list and it should be fairly clear which ones apply to your proposal, especially if you would go through the list with another person that has read your proposal.“