A possible subtype system

The basic concept is as follows.

You have two types, a primary and a secondary.
Your primary style determines your passive ability.
Your secondary style determines your active ability.

You may not have two different types from the same category, but you may take the same one twice.

Elemental Type:

Passive: As Current Fire

Ability: Convert. Convert anyone one chip attack to Fire element. Once per turn.

Passive: As Current Wood

Ability: Convert. Convert anyone one chip attack to Wood element. Once per turn.

Passive: As Current Elec

Ability: Convert. Convert anyone one chip attack to Elec element. Once per turn.

Passive: As Current Water

Ability: Convert. Convert anyone one chip attack to Water element. Once per turn.

Weapon Type:

Passive: Marksmanship. Increased accuracy by 1 rank with Shot type attacks, even when under the influence of status down effects. Accuracy with Shot type attacks can surpass A rank.

Ability: Snipe. Add Seeking to the next action as a free action. (Once Per Turn)

Passive: Sword Mastery. All Slashing attacks an additional Accuracy rank.

Ability: Swordplay. Free action parry/dodge after 2 consecutive Slashing attacks. (Once Per Turn)

Passive: Mass Destruction. All chips with area of effect abilities (Blast, Nova, Splash, Spread) have their area of coverage upgraded one level.

Ability: Smash. Add Break to the next action as a free action. (Once Per Turn)

Passive: Melee Mastery. All Melee attacks gain an additional Accuracy rank. Does not apply to Slashing attacks.

Ability: Bash. Add Impact to the next action as a free action. (Once Per Turn)

Ability Type:

Passive: Medical Mastery. Changes the cost of Healing to 1:1 (1 HP for 1 point).

Ability: IV: As a free action, attach an IV pack to an ally that heals 5 HP per action. The IV pack breaks upon taking a hit and can't be used for the rest of the battle afterwards on that ally. (Once Per Turn)

Passive: Debuff. Support chips with a + in their names, Buff, and Strengthen may be used on an opponent as damage reduction instead. Support chips reduce all damage for the rest of the battle, Buff reduces all damage up to its given point, and Strengthen reduces damage for the next single attack. Only one instance of Debuff can be on each target at any given time.

Ability: Buff. Add (Level + 10) damage to any one chip attack or SP's regular attack as a free action. (Once Per Turn)

Passive: Blueprints: The ratio for an object's point cost increases to 4:3 (Giving you 4 points for every 3 you spend. Example: NaviA puts in 90 points and gets a 120 point object).

Ability: Masterwork: You may add 20 + (Level) HP to an object's max HP as a free action. This can not be used on the same object more than once. (Once Per Turn)

Bug: Bug type Navis are the weirdos of the Net. Oddly coded, oddly executed, and just plain odd. Their lack of cohesive programming makes them useful in that many Navis have little in the way to combat their strange brand of fighting. Bug type Navis rarely have to fight their opponents in top form due to negative statuses.

Passive: Infected. Bug type Navis gain a free instance of the Glitch signature effect to use for signature attacks once every five levels. (Starting with Level 0.)

Ability: Randomize. Activate as a free action on an attack chip or an SP's regular attack to randomize its damage dealt from anywhere between 1 and double its original value. (Once Per Turn)

Combat Type:

Passive: Stealth Encoding. You are a lower priority target than other allies, and are more capable of successfully hiding with a non-standard action.

Ability: Ambush. Add Phasing to the next action as a free action. (Once Per Turn)

Passive: Airstep. When you jump as an action, an updraft is created beneath you that launches you into High Altitude. The updraft dies down when you land, but while it is active, any non-Melee or Ground attacks can be caught in the updraft and blown up to you.

Ability: Gust. As a free action, you gain one instance of Knockback or Pull. This can be added to an attack, or used freely on it's own. (One Per Turn)

Passive: High Gear. Speed types Navis gain a 10% bonus to Base Evasion. (This is their evasion value before RP, Statuses, Movement, and Dodges are factored in. Not Applicable in some situations.)

Ability: Afterburner. Sacrifice 1 action from the next turn to add 1 additional action to this turn. Sacrificed action carries over between battles. Can't be used on subsequent turns. (Once Per Turn)

Passive: One for All. Damaged inflicted to an ally/allies is evenly split between you and them. An ally must consent to this effect before it counts them as an ally. You can have 1 + (Level/10, rounded down) allies connected to you at any time.

Ability: All for One. Navis and SPs may transfer a Battlechip from your folder to an allied target as a free action. Note: SPs with this ability may receive one Battlechip directly from the Operator each turn. (Once Per Turn)

Shift Type:

Passive: Terraformer: Ground Navi's Terrain altering signature costs are changed to: (Small costs 5, Medium costs 15, Large costs 30, Stage costs 60)

Ability: Anchor: When named chip attack or SP regular attack hits, it causes the target (limited to one) to be unable to come off ground, or fly. Disables floatshoes, if the virus/navi has it. Lasts one turn. (Once Per Turn)

Passive: Gain 1 additional maximum folder size every 5 levels, starting at 0.

Ability: Remove or add any one NC program as a free-action, once per turn. You must have sufficient space to load new programs.

Passive: Defender. Shield type Navis have an increased chance that impromptu RPed defense actions, such as parrying with a weapon, will succeed.

Ability: Reinforce: Add 1 + (Level/20) Hits to an existing shield as a free action. The same shield can't be Reinforced more than once. (Once Per Turn)

Passive: Vigor: HP Memories grant an extra 5 HP per upgrade. SP HP Upgrades grant +5 HP every other upgrade, starting with the first.

Ability: Gatling Attack: Free action Buster Shot/SP regular attack after two consecutive Buster Shots/SP regular attacks. (Once Per Turn)
Already considered something like this.
Eh, I like the current system the way it is.