spoilers ahead, Starbuck.

• Mulder would have fewer absences (post-abduction)
• more Mulder and Doggett (and Scully) episodes
• no Doggett and Reyes episodes—did anyone even watch those?
• at no point would Scully's pregnancy put her in danger
• Scully would have said, "William, after our fathers"
• Scully would never have had to give up William
• the cigarette smoking man would have (a) had nothing to do with Scully's pregnancy and (b) died when Krycek pushed him down the stairs, or at least when he was blown up
• the Lone Gunmen would never die, because what the fuck?
• the alien story arc would be properly put to rest, and the last two series would be monsters of the week all episode every episode