I personally was upset when Fallout 3 didn't have Weapon Modifications and Ammo types, however FONV did. However, the construct-able weapons that were in Fallout 3 were not in the game as a trade off. Do you guys think that they should both be in the game or not?

I do. But I'm sure Obsidian wanted to be original and not copy everything from Fallout 3 into Fallout New Vegas. I guess they wanted to make Fallout New Vegas to be a "brand new" experience to a Fallout game.

I hope both return in greater number in Fallout 4