referring back to a comment further up, I think dark angels should get a bonus to librarians and Chaplains (if they become a thing in the game)

That would definitely be fitting!

I would hope that the Space Wolves and Blood Angels get unique abilities for the Apothecary Class. Since their Apothecaries are rather unique lore-wise, I think it would only make sense. Though depending how they did it, They could easily end up with unique abilities for each Class and Chapter combination. It would greatly help to make the Space Marines less.... whats the word... Same-y? I can't think of a better word right now.

Blood Angels: Angels Decent - Increased melee damage for X seconds after landing using a jump pack.

Space Wolves: Fury of Fenris - Increased movespeed and health regeneration with every connecting melee attack for X seconds.

Ultramarines: Guilliman of all trades - Recieve a bonus depending on what loadout you're using for X seconds. (Assault, Tactical, Devastator, etc.)

Dark Angels: Archeotech - Costs less requisition when bringing/purchasing relics onto the battlefield.

I think he may have meant less costly termies 'cause DA have a full company of them, which is rare for a space marine chapter.

Blood Angels obviously need some kind of buff to their assault playstyles even if it is only cosmetic in nature.

Ultramarines are rigid when it comes to codex tactics, perhaps some kind of ranged/organizational bonus with regards to deployments?

Dark Angels plasmas all the way

Wolves ...Just give them all axes and jump packs.

I would say to give them a buff that relates to the chapter Primarchs's curse, such as the Blood Angels Red Thirst. Maybe such chapter traits should do something that is more of a general benefit, like the Red Thirst being an accumulative melee but the more you kill in melee; the buff would be active for a short time but would vanish and have to be re-accumulated. This would obviously be best suited for those melee specialties but could still be used by, say, a Tactical Marine.