An advantage would be that besides his knowledge of how DC works, he's gotten very good at being a pro-Trump voice with the media. Another asset would be that the dems probably don't have a potential VP choice who could measure up to Gingrich in a debate.
That being said, I look forward to Trump's well thought out and maybe unexpected choice. I could see an advantage to having a younger guy (pandering for the female vote would be counterproductive) who Trump could mentor.
Gingrich is too old. He’s 73