Space Marine 40K army building

After a long time of absense from 40K playing I am back. After a Tau army (the old days), I now want to field a Space Marine army. I started to build a Grey Knights army but then I followed the dark path of custom Chapter. So far I read the fluff and trying to finalize my army's color scheme. I have already built a basic backstory and I am working in a custom codex. It is a difficult process, especially if I want to make the codex balanced. If I wanted an OP army I would have stayed with the Grey Knights, haha.

So here is my backstory so far.

"When the Titan moon was in the Warp and the first full Grey Knights were off the last stages of training, their Monastery received a help signal from a convoy of Astartes ships that have fallen to a Warp storm chasing some Traitors. Since the convoy was with several Legions the GK council decided to send a very small team with the new GK to also test their potential and save the gene-seeds of the Astartes from possible annihilation and corruption from the Traitor Legions. The corvette found the convoy and organized them to return to the monastery but a sudden Warp storm wave made things worse and made them lose their way. In the following millenia the convoy drifted in the Warp trying to find an exit. In the way the GK guided the Legions and purged Traitors and heretics found in various places and planets there. They also encoutered Loyalist forces lost in the Warp and found that they were not tainted yet. The new team had to adapt to the new situations with the Warp environment, limited supplies and loss of battle brothers and crew. The GKs died in the battles and the original Legions were almost decimated. However the guidance and legacy of the GKs remained and new neophytes trained. Finally, after a very long road, only one Battle Barge remained, with salvaged parts from all the other ships and parts from some Space Hulks and tech found in lost Forge Worlds. The saved Mechanicus played a vital role in saving the crumbling ship.

The Battle Barge and the remaining force within exited the Warp in the Purge of Jollana (913.M41) when the attack of Ahriman loosend the barrier between the dimensions. They responded ASAP to the

battle of the planet and fought a furious battle in the Library, yet not in a vital place as the GK were.

After the battle they reunited with the Imperium forces. The Inquisition was suspicious at first, but

after a long process it found that the team was pure. The force could not become GKs, so the Inquisition and GKs given them the privilege to go to other Chapters or found a new one. Most of them chose to make a new Chapter with the name "XXXXX" (working on this), to honor their first Chapter Master. His story goes that while they fought a huge battle in a Hell-Forge World, he was lost to a cavern and was saved by dragging himself from a fox´s tail (minor feral daemon). The liquid bronze of the soil stained his armor. After his emergence from the cavern he managed to find his battle brothers and succeeded to organize a defence and they were saved. After this battle all the battle brothers have painted their armor Bronze-Brass color. The remaining Legion SMs went back to their homeworlds, yet still remained in contact with the new Chapter. Also the new Chapter, in order to honour them, organized regular visits to the monasteries and planets of these Legions-Chapters.

The saved armors of the lost GKs and SMs, along with the untainted gene-seeds, were given back to their corresponding Chapters and the "XXXX" started a path to the far fringes of the galaxy to bring the light of the Emperor. They passed the Ghoul Stars and finally they settled their homeworld in the Eastern Fringe (Scutum–Centaurus Arm, Vulpecula constellation). There they found a ringworld (Hey, the 40K has a Dyson Sphere, so I am not outside the fluff here ) inhabited by humans and helped them eradicate the emerging Necrons from the world. The ringworld is older than the Necrons and the Old Ones and the War in Heaven. The Chapter stayed there, as the mechanicus wanted to find the archaeotech the ringworld had. The armor will be a mix of Greek Hoplite and Monks with other bits. The Knighthood of the ringworld will be not based to the wester type of arthurian style but to the japanese kanto style. The Chapter will accept the new ways, a mindset that they keep from their Warp crusade (check their battle cry below), yet they will still remain faithfull to their Father and Emperor. 

So far I am at this point. I want to make the Chapter a mix of GKs, Exorcists and Blood Ravens-

Thousand Sons, as they want to be as pure as possible from the Warp and that they consider knowledge a high standard. I am also thinking of using a modified GKs codex as a force construction but I don't know if this is possible by GW rules. I want to battle a close combat army with heavy support at the very back. (A remaining from my Tau days? Possibly)

Battle cries:

"Improvise, Adapt, Overcome"

"Vir sapiens et fortis est et vir doctus robustus et validus"

Gene seed: unknown, possibly Dark Angels

Primarch: unknown

Loyalty: loyal

Colors: Bronze-Brass armor with black runic details and Red-Purple or dark blue tunics

Founding: 2nd or 26th, unknown because of

Warp

I started building the army for Blood Ravens so I used the basic Codex Astartes to form a basic structure"

The army will have features of hoplite armor, as the helmets and chest plates, along with other parts of their gear. Also some minor details from japanese warriors, especially the overlapping design of the armor plates. Something which was also prominent in many armies of the ancient western world. Most of the nomenclature will be Latin to be close to Imperial High Gothic.

Basic Tactical Marine

Some WIP names for the chapter:

Equites Austi

Equites Volpii

WIP names of the ringworld:

Corona Exitus

Corona Terminus

Orbis Exitus

Custom Bulpup Bolter, some working names: Groza Pattern, Oberndorf Pattern, Schwarzwald Pattern (Have made a model and trying to make some casts)

A WIP chapter badge.

I want to make part of the army to be a Penance Squad. Rules could be like the Sisters Repentia rules? They will be Battle Brothers that with some way have ashamed the chapter or themselves to the eyes of the Emperor. Maybe sole survivors from their team or failed to save a world or something else. Will wear monk robes and only their chest plates, along with the power melee weapons and shields· they will carry the rest of their armor strapped to their backs, like in the Mission movie (1986) with Robert De Niro.

Because so far I have a small fluff knowledge, I would like any input. Thanks in advance!