Consider starting with him at Springer, with the idea you’ll hike with him as long as you’re both enjoying it (that means enjoying the hard times too - a perverse sort of enjoyment, to be sure).
Then get off if/when it’s not your cup of tea, and run trail support, like Queen Diva did this year. By the time you get off, you’ll have many new trail friends of your OWN, since these incredible, deep bonds can form early on. You’ll see them all the time at trailheads and in town. They’ll be YOUR firends too, and these friendships last years and years (so get in on the ground floor, and you’ll never feel left out).
You’ll also know exactly what “the life” is like and won’t be prey to an over-active imagination.
I would not suggest getting back on the trail as a hiker later on, because by then a strong forward momentum is formed. Don’t underestimate this momentum. There is an urgency to keep going, and it’s not personal. You won’t be in thruhiker shape either. Maybe hike together for a day or part of week, tops, in this situation.
It could be, with a can-do attitude, the adventure of a lifetime for you both. Trust me, if you do trail support, yours will be the most welcome face on the trail! 
Jan LiteShoe