I don't see the point of that. A 50-year-old doesn't need a godparent.
No, you don't need a godparent in the way an infant does--to speak on his behalf--but having a godparent is still important. Ideally, that person will be a help and support to someone in the process of conversion and afterwards, and at baptism/chrismation stands with you as you participate in the sacraments. That person, in a way, represents the entire Church standing with you, supporting you, and receiving you as a member of the family of God. I suppose you could speak to a priest if you had an adamant opposition to this and see how that goes. I know of at least one case where the person converting never chose a godparent, and the priest forgot about it, and so he just asked one of the regulars to do it, and it worked out.
If none of this stuff effects a change in the person, then what is the point? Is it just for the music and the singing? Studying scripture and doctrine, and then verbally dissecting all that for hours on end? Reciting generic scripted prayers? Nobody gives up their porn, their beer, or their bongs, so what does all of this stuff really do?
I seriously need to talk myself out of this.
All of the things I bolded above are wonderful things, things God has given us in one way or another in order to help us become holy, but they can be misused, abused, or unused. It's up to each one of us to receive what God has given us and put it to good use. If we don't use these things in the right way, we don't benefit. But that doesn't mean that these things are useless or bad. Many people put them to good use in their own lives to the best of their ability and derive benefits, whether we see those benefits easily or not.
All of us are sinners, we struggle with different things, and our healing takes its own course because God is guiding the process. It's not a matter of "confess once a month, commune once a week, fast twice a week, pray twice a day" and everyone experiences the same degree of healing and change. Some people repent and keep growing stronger and stronger, others repent and fall, rise and fall, rise and fall, a thousand times. We should pray for others, support them, and trust God to be merciful with them, and focus on our own repentance and healing.
So if someone is going to consider joining the Church because it has such great riches and s/he wants to observe how other people (fail to) put them to good use so that s/he can question the Church's validity, s/he should go right ahead and talk himself or herself out of it. I'll talk them out of it. Many of us will. If that's how s/he approaches it, it will never work because s/he's not doing it right. But if s/he's going to consider joining the Church, I'd tell him/her to do it because s/he loves Christ, because s/he loves his gospel, and s/he can't imagine being anywhere else but with him. But be aware that Jesus has always and unapologetically hung out with "questionable" friends.