I'll give it that it's cool to wield a one-handed chainsaw, but as it has printed on the side it was a tool for the US Army... Praticaity "in my humble opinion" dictates that it was perhaps a tool before the bombs fell to cut through Constantia wire and other defense when assaulting Chinese held positions. As a actual melee weapon I just can't see it being used unless in power armor or as a last resort. If your getting close to a target you'd want something like the combat knife or trench knife "miss my little shabby friend from FO3 OA" because you'd want to do the deed quietly... Anybody have any information that I don't on the subject?

Also why can't I have a full sword conversion so I can go full on ultra Marine on these raider heretics.

The Serrated or Stealth Blade attachments to the Combat Knife make it pretty much identical to the Trench Knife, sans the knuckle spikes on the grip.

As for the Ripper, one loading screen describes it as being used as a close-combat weapon for American troops. It wasn't meant as a stealth weapon, it was meant as another brutal melee weapon like the Super Sledge... and American Troops were probably using it in Power Armor, too. In Fallout 3 you'd have unarmored Enclave officers using it, though.

Would be nice to make it a full 2-handed chainsaw. My Doomgal character would certainly appreciate that.

It was used for delicate surgeries.