I would like to see Steam integrate its workshop into NV. I also would love to see a semi-realistic mod that did away with giant bugs and have more realistic looking factions, a bit like the tv series "Revolutions".
Fallout wasn't about realism. If it was, the first game wouldn't have giant bugs, The Master, supermutants, ghouls, etc. Radiation would be more than just an annoyance cured by Rad-X\Rad-Away, and half the weapons wouldn't exist.