"Okay, well. Both of us want the other to become the replacement parental figure so we can finish high school, right?"
"Finding where you hid the revert button would make this much easier on both of us."
"I hid nothing. It would be nice if you realized Jeff's master profile was set up when the device came online. So, you not having hours of hands on experience indicates you are the copy and should accept becoming dad again."
"Or you did this to me and altered my profile to trick me into falling for your trap?"
"If I had that much time alone with your profile and the Chronivac, you would be happily volunteering to turn into dad, right? I'd know dad needs to come back, we would both have the same claim and we don't want to miss out on our 20s. I'd have made you overly excited to permanently become my dad. And you would have seen it in the history."
"I don't believe you didn't do something to me, you say you ran outside, but I think you ran back and turned me into a you. So even if I was Mike, I think you caused this chaos and should be punished. Then you messed with the history to make it look like it was done alone. Either way, our conversation isn't getting us anywhere. We need a way to apply the changes to a single target randomly." Both Jeff's begrudgingly agreed, feeling the other Jeff was being unreasonable and not seeing logic.
"Ugh. Here!" Jeff who remembered exploring the machine after school pulled up the template option and began throwing in traits and details. "We can just program the changes or the end result into the template and then the template gets applied to a profile. So we can set his wait to be 230 lbs, or make it so whoever is targeted will gain 70 lbs. However we want to do it."
The Jeff's began working together to define the kind of dad they wanted to have, and though neither wanted to become the dad, what kind of man they wanted to become if they had to. They agreed their dad's new age would be 34, 18 years older than Jeff and the youngest one of them would be able to remain. They, both being Jeff, liked the idea of the new Mike focusing on having fun and settling down now that Jeff is just 2 years from adulthood himself.
Mike would be an easygoing, mostly social smoker, drinker, and stoner, occasionally indulging alone. This would allow him to more easily adapt to any crowd and let Jeff feel like he doesn't have to give up his experimental phase if he looses this coin flip.
Most 26 year-olds aren't ready to start a family, let alone have an 8 year old, so Mike's history was spotted with frequent hookups, and the few relationships he did have lasted a few months before the complications grew to be too much.
They added knowledges, a job and job history, hobbies, and habits. Original Mike's friend group wouldn't know the new Mike, so they started adding friendships, a slew of ex girlfriends, and sexual experiences. Mike's morning black coffee will remain a constant, though both Jeffs hated coffee, household maintenance and chores they decided to ingrain as routine so whoever became Mike didn't accidentally let the house fall into disrepair. Sports interest would remain, as well as a love of cars and other "classic" male passions to make Mike relatable in a bunch of ways.
They finally circled back around to physical traits and gave Mike traits they liked. Easily adds muscle mass, tendency to stay lean, resistant to cancer and age related illness, no allergies, won't go bald, won't start graying till mid 40's, and rapid beard growth. A long weekend without shaving and Mike could have a respectable short beard.
Original Jeff saved the template and made a new one for he who will remain Jeff. After some minor back and forth they decided Mike will be unaware and have no memory of being Jeff or the Chronivac. The transformation would take 2 hours and beyond turning one of them into Mike, Jeff's parentage is shifting with Mike's new history and traits and Jeff will remember everything...
Original Jeff tried one last time to convince the other Jeff that he should really be Mike. Jeff's final request was that if he does become Mike, Once Jeff is 18 and doesn't need a father, to be brought back to his 20s as an older brother.
The system was loaded and ready to randomly choose who becomes dad and who remains son.