There aren't even any passive resistance mods for suits yet. No need to rush to active mods without a passive mod to do the same thing.

Aside from the obvious ones (increase gun damage, decrease damage taken, etc)

Kinetic Overclock:
Greatly increases movement speed, sprint speed, and a stamina for a set duration. If a setback is needed, the user could have reduced max stamina and stamina regen for some amount of time after the module enters cooldown.

IFF/Tacnet Disruptor:
Turns the Tacnet radar into static and disables the ability to discern friend and foe (Reticle doesn't change color, health bar doesn't appear, etc.). Pretty useless in modes with friendly fire disabled (though watching a bunch of reds go around shooting each other would be amusing) but can potentially be very useful in the new SoonTM FW and PC.

Tacnet Broadcaster:
Increases the users passive scan radius and scan precision while also broadcasting the results to teammates. Comes at the cost of revealing their location to all enemies within the users scan radius.

I've got a few.

Hardeners for armor and shields- Offers a fixed % across all tiers, and each tier has lower recovery cooldown times per tier, skills would reduce the cooldown by X% per level. The armor variant would slow the user down by X% as it's being used while the shield one would increased shield recovery times by X% while in use, this would be to prevent abuse.

Active Cloak- Makes user invisible until they fire/use a weapon unless it's standard melee, with a high fixed cooldown recovery time per tier and an increased duration as one goes up the tiers, skill level would increase duration by X% per level, movement would disrupt it's effects, reducing it's effectiveness, the faster one moves, the move visible they are.

Active armor regen- A one shot quick burst heal to armor, that gives a fixed amount over a small fixed period of time with increased armor recovery amount as you go up the tiers, would also include 3 variants, Light-Provides less armor but recovers faster with lower equip cost, Heavy-Provides more armor but over a longer period of time with higher equip cost, and Standard, skill level would would increase the speed armor is restored by X% per level.

Active shield booster- Provides a fixed amount of shield recovery in an instant, with reduced returns compared to the armor variant, with a fixed amount of shields restored across all tiers, with 3 different variants Light- provides less shields but recovers faster with lower equip cost, Standard, and Heavy- Provides more shields with a higher cooldown time and higher equip cost, skill level would reduced cooldown recovery time by X% per level.

Weapon over-clock- Would only work on weapons with overheat and feedback damage capabilities, it would increase the weapons damage output for a short period of time by a fixed X% while also increasing it's heat generation and feedback damage by X% for a shot period of time, duration time would increase across the tiers with a fixed recovery time, skill level would increase duration X% per level.

Coolant dispersion- Only works with weapons with overheat features, would increase weapon heat recovery/overheat recovery (Will not effect heat generation) over a fixed amount of time, heat recovery rate would go up across tiers, skill level would increase the duration X% per level.

Tageting assist module- Only works on weapons affected by aim-assist based based weapons, upon activation a targeting circle appears around any enemy within a fixed range, circle size is determined by the targets distance, all shots fired within the circle forces a hard aim-assist within the target circle, shots are unaffected by player sim so head-shots are unlikely, target acquisition is different across tiers and types, Close range-Faster acquisition with longer duration and lower equip cost, but has longer cooldown time, smaller target range and smaller target circle, Long- Has greater target range and has a smaller target circle, but has higher equip cost, longer acquisition time, and a shorter duration, skill level would reduce the cooldown recovery time X% per level.

This is some of the stuff I think would make the game a bit more interesting, anyone else want to add?

Aside from the obvious ones (increase gun damage, decrease damage taken, etc)

Kinetic Overclock:
Greatly increases movement speed, sprint speed, and a stamina for a set duration. If a setback is needed, the user could have reduced max stamina and stamina regen for some amount of time after the module enters cooldown.

IFF/Tacnet Disruptor:
Makes the Tacnet radar display static and disables the ability to discern friend and foe (Reticle doesn't change color, health bar doesn't appear, etc.). Pretty useless in modes with friendly fire disabled (though watching a bunch of reds go around shooting each other would be amusing) but can potentially be very useful in the new SoonTM FW and PC. Edit: Disables for both user and reds (possibly blues as well)

Tacnet Broadcaster:
Increases the users passive scan radius and scan precision while also broadcasting the results to teammates. Comes at the cost of revealing their location to all enemies within the users scan radius.

This is some of the stuff I think would make the game a bit more interesting, anyone else want to add?

I believe CCP has said they won't make anything that makes dropsuits any faster cause of the speeds we can already reach, I like the idea of the Disruptor, but I think it should only affect enemies within a fixed range of the user and and the effects would become stonger as you approach the user, maybe have different variants like a long range one that has the drawback of effecting allies to a lesser extent. I like the broadcaster idea but it sounds too similar to the Scanner and would really make much sense to both and I couldn't really see much of a drawback for having one outside of equip cost.

I've always heard the max speed limit was due to the hit detection. Hit detection has made leaps and bounds since this was said so I'm hoping CCP now can allow for much higher movement speeds which would allow the overclock to function without being game breaking (along with a buff to base scout speed).

I intended for the disruptor to have a limited range (~100m?) and give the full effect instantly so long as your precision beats the enemies scan profile. One explanation for this would be that the disruptor isn't a jammer but rather a virus that disrupts the enemy's connection to the TACNET but for the disruptor to target the enemy, it needs to know they are there, hence the precision/profile condition.

True, the broadcaster is kinda useless with the scanner, but the scanner very severely needs a nerf (no spinning/sweeping, no error messages, and a much higher cooldown) which would give room for the broadcaster to function.

Siege Module for heavies

I'm not sure what that is, would you mind explaining?

In EvE there is a certain kind of ship that can fit a Siege Module. A Siege Module, when activated, immobilizes the ship and greatly increases the offensive and defensive capabilities.

Here's a link.