As others here I am not really contend with how the IF came out, so I thought I just elaborate a bit on one of their least known successor chapters, taking into account what's written in RoB, add a bit DYO Chapter and a bit about how I'd like them to be.
This is what came out of it:
Hammers of Dorn
Imperial Fists Successor
Colors: Black with gold
Chapter Characteristics Modifier: +5T, +5Will
Chapter Demeanor: No Mercy, No Respite
Combat Doctrine: Siege
Solomode: As IF
Squad Mode Attack Pattern: Siege-Breaker
Squad Mode Defencive Stance: Courage under Fire
Chapter Homeworld: Fleet Based
Divergent Chapter: More Devastators and heavy Armor
Advances: As IF
Battle Cry: Captain:"He is the anvil!" All:"We are the Hammer!"
Chapter trappings:
Devotional Hammer (Like Ceremonial Sword but +2Dmg -Balanced)
Aiguillettes and Lanyards:*
These ornamental braided cords exist in different materials,
each representing another trait.
They can be worn from shoulder to Chestplate or connected to the sidearm.
Gold: +2 to Fellowship tests
Silver: Works as a charm
Squad colors: The kill-team restores 1 bonus Cohesion for every Primary Objective achieved.
Starting Talents:
Rival (Ultramarines)
Hatred (Word Bearers)
*I hope I got the right Names for those Chapter trappings. English is not my native language and it took me quite a while to find those words.