My one would be a corrosive Vault Hunter. Fire (Sirens, Krieg), Shock (Sirens, Soldiers, Gaige), Explosive (Brick), Ice (Baroness) are already used by other characters and I don’t consider SLag an element, but rather mining trash. The only thing left is corrosive, and it has some great potential. I will explain my idea for a skill tree below. I use Pre-Sequels Skill tree as a template.
Action Skill: 8th Plague
Release a swarm of Locusts, which attack your enemies, inflicting normal and corrosive damage. Spreads up onto multiple enemies, damage decreases by 10% for every enemy attack at once. Enemies attacked by them panic, which decreases their damage resistence by 2% per second and their accuracy by 50%. Increases your melee damage by 300%.
Your locusts can be shot down, which decreases their damage potentialand your action skill time. Your melee damage increases when your action skill time decreases.
The Hive mind tree adds additional Insects. You can choose, which one you will release, but you can only release this type per activation.
Furthermore, as long as your action skill is active, you can stack unlimited amounts of corrosive DoT’s onto your enemies. E.g., you shoot your enemy twice with a corrosive gun, you will inflict two seperate corrove DoT’s. But every following DoT will inflict 50% less damage than the DoT before it.
Duration: 15s
Cooldown: 45s
Melee damage: increases up to 600% maximum.
Deadly Poison
*Injection /5: Increases damage from corrosive sources by 20% per level. Decreases gun damage by 10% per level.
*Corrosive Flower /5: Kill Skill - Increases chance for corrosive DoT by 10% per level.
*Poison Fang /5: Increases melee damage by 40% per level, also adds Corrosive Damage Rank +1 per level.
*Toxic Waste /5: Increases splash range from corrosive weapons by 10% per level. Slows porjectile speed by 10% per level.
*Spreading Infection /1: Every opponent spreads his corrosive DoT to allies when he is in radius of 5m around them.
*Entomophobia /5: Kill Skill - Increases Action Skill time by 3 seconds per level. Decreases cooldown time by 2 seconds per level.
*Crawling under your Skin /1: You regenrate life equal to 30% of your corrosive damage.
*Rattlesnake /5: You gain a stack of “Poisoning” for every DoT of Corrosive damage inflicted. For every stack, your corrosive and melee damage increases by 0,2% and your gun damage decreases by 0,1% per level. Can be stacked up to 999 times.
*Poison Touch /5: Enemies with corrosive DoT’s on them stack up “Death Wish”. They gain 1 stack per second. For every stack on them, their damage resistence against corrosive damage is decreased by 2%, their accuracy is decreased by 3%, but their damage is increased by 4% and their gun damage resistence is increased by 3% per level. Your FFYL time is increased by 2 seconds per level.
*Insect Plague /5: For every enemy with a corrosive DoT, your Action Skill cooldown time is reduced by 1 second.
*Pestilence /1: Your corrosive damage is unresisted. Every DoT of your corrosive damage generates another DoT. You can generate 1 additional DoT per second.
How is it played: Obviously, this tree is a DoT tree. Your gun damage is greatly decreased, while your melee and poison damage is greatly increased. You will feel, how weak the enmies will get, when they are poisoned. The aim is to activate your AS nearly all the time.
Hive Mind
*Strong Jaw /5: Your locusts will inflict 5% more damage per level.
*Armored Maggot /5: Adds one armored Maggot to your action skill wheel per level. Armored maggots will stick to you, protecting you from 60% damage inflicted to you. They die after getting damaged too much.
Chitin Armor/5*: Your armored maggots can withstand 5% more damage per level.
*Poison Pouch /5: Your armored maggots will spit acid onto enemies near to you. They will regenerate life equal to 5% of the damage per level.
*Arachnophobia /1: Adds a gigantic Tarantula to your action skill wheel. Tarantula will jump onto your enemies, knocking them down and inflicting a massive corrosive DoT on them. Rank +6 corrosive DoT.
*Runner up /5: Increases movement speed of you and your tarantula by 10% per level.
Paralyzing Bitec/5*: Your Tarantula will inflict a paralyzing bite to grounded opponents, which prevents them from standing up for 0,5 seconds per level.
*Vengeful Hornets /1: Adds a Hornet swarm to your action skill wheel. Vengeful Hornets will fly around you until commanded to attack an enemy. WIll protect you from Elemental damage when around you, will inflict the last elemental damage they intercepted onto their enemy.
*Hot Swarm /5: As long as your Hornets are around you, your fire resistence increases by 20% per level.
*Corrosive Bite /5: Your Hornets inflict additional corrosive damage to their normal damage/stored elemental damage. Rank +1 corrosive damage per level. If they stored corrosive damage as last damage, the corrosive damage they inflict is increased by 20% per level.
Midnight Moth: Adds a gigantic Moth to your action Skill wheel. When deployed, Moth will spread an acid smokescreen, which inflicts +6 rank corrosive damage to all opponents standing in it. Moth will attack enemies automatically, inflicting massive damage. Moth cannot be killed. Duration for this one is 25s and cooldown is 70 seconds.
How is it played: This is your pet skill tree. I wanted it to be in contrast to the regular pet classes like Mordecai, Wilhelm or Axton by adding different insects for different situations. In my mind, Midnight Moth should be your last resort option, as it is extremely fast and extremely deadly, clearing rooms filled with badasses in seconds. The rest is for specific enemies.
Nimble Reptile
*Slime Sliding /5: Increases your movement speed by 20% per level.
*Acid Armor /5: For every corrosive DoT you inflicted on your enemies, you gain a stack of “Acid Armor”, which increases health capacity by 0,2% per level. Can be stacked up to 200 times.
*Poison Cure /5: You regenerate health equal to 2,5% of all corrosive damage you inflict.
*Reptilian Plates /5: Decrases shield capacity by 10% per level, as well as increases health capacity by 10% per level.
*Poison Hunter /1: All your damage you inflict is calculated by your movement speed. For example, if you walk with 10% movement speed, you will only inflict 10% damage. All damage buffs are calculated with this.
*Acid Feet /5: You will left corrosive footsteps behind you. Every enemy walking into them gains a corrosive stack. Rank +1 corrosive damage per level. Increases movement speed by 20% per level.
*Brain Damage /1: Your movement speed increases by 1% for every corrosive DoT you inflict onto enemies. If you have no DoT’s inflicted, your overall damage is reduced by 50%.
*Self-Restraint /5: Movement Speed decreases by 10% per level, but increases yor damage from all sources by 15%.
*Assassination /5: Attacking an enemy from behind with a melee attack increases your melee damage by 100% per level.
*Stealth Hunter /5: Kill Skill - increases movement speed by 10% per level.
*Maximum Efficiency /1: If your damage is reduced by a source, this reduced damage is doubled.
How is it played: This is the tree for people, who think, that even Zer0 is too slow for them. You will gain extreme Movement speed, but you need to exploit it to inflict damage. All movement buffs will vanish after a very short amount of time, so you need to calculate your every move, so you can always kill something and be fast enough.
I hope you like this idea, let me know your thoughts about it 
-Glacier
