Good, keep reading, Jimmy!
I thought there are way too less Skyrim armors in Fallout 4...After I learned how easy it actually is...well I thought again why the...?!?!
So I converted a few on my own.
If you know how and get used to it, you can convert your favorite armor whithin 20 minutes or less...
I didn't get permission for a few armors I ported from Skyrim, so I can not upload them here for everybody to use.
I can however show you how to do it yourself =)
All you need is:
BodySlide and Outfit Studio for Fallout 4
Material Editor
(I might do a full tutorial for that later; but no promises)
Very short impro tutorial for Fallout 3/NV:
1. Open armor in nifskope
2. expand the 0 NiNode and click on the NiTriStrips of the armor piece you want
or just click on the armor piece in the 3d window
3. click file -> export -> export .obj
4. repeat with every shape until you have every armor piece you want
5. continue with step 10 of the tutorial
The steps stay the same, but because Fallout 3 armor use other body types you will have to move and adjust them way more than the Skyrim armors.
THERE WILL BE AT LEAST 1 ARMOR FROM SKYRIM I HAVE PERMISSION TO UPLOAD... HOPEFULLY SOON :P

Want to convert gloves as well?
Good luck with that!!
A suggestion, how I did it, can be found in the optional file.
IT IS FAR FROM PERFECT!
REMEMBER: PORTING ARMORS FOR YOURSELF IS FINE. YOU CAN PORT WHICHEVER AND AS MANY YOU WANT.
BUT YOU CAN'T SHARE/UPLOAD THEM UNLESS YOU HAVE THE PERMISSION FROM THE ORIGINAL CREATORS.
PLEASE KEEP THAT IN MIND!
FOR THAT REASON I CAN'T AND WILL NOT SHARE MOST OF THE ARMORS IN THE SCREENSHOTS!
THESE ARE ONLY TO SHOW YOU IT ACTUALLY WORKS AND IT LOOKS AWESOME.
I'm on patreon now:

CHEERS GUYS
Armors in the screenshots are:
Seraphine Armor - CBBEv3 - UNP by BloodFree
Merta Assassin Armor UNP - CBBE by Deserter X - Mitosuke (used in the tutorial)
Zerofrost Valkyrie Armor
Black Viper's Will - UNP-CBBE by redtox (will be available for all; hopefully pretty soon)
Ghost bodysuit for Type3 by Fizz (last image; ported from Fallout 3 | Outfit Studio crashed (my fault) shortly after I saved it first, I didn't do the rest again since it was only a demo to look if it works with Fallout 3 armors as well)