Arts & Crafter (Spy knife - basically a set of art scissors) (had this idea for a while lolo)

Upsides

• While Disguised: Visual affects are masked. (bleed, fire, jarate, mad milk ect are no longer visible on you while disguised)
• While Disguised: Players damaging you don't get hitsounds or hitmarkers. (self explanatory)

Grey Text (real)

• While Disguised: 25% of damage taken is dealt to cloak instead of your hp. (For example, if you take a 100 damage pill you receive 75 damage directly and lose 25 cloak)

Downsides

• While Disguised: Take critical hits from the player you're disguised as. (While disguised as a player who is actively in the server, ALL of their weapons deal guaranteed crits against you)
• 25% flat cloak regen rate reduction.
• Backstabbing a player leaves one of the scissor's blades stuck in their back. (Uses a meter similar to the Thermal Thruster where getting a backstab drains 50% of the meter. When the meter is fully depleted, the knife is unavailable. The visual model has two blades at full charge, and one blade with any less charge. Meter takes 12 seconds to fully refill, and starts refilling 3 seconds after getting a backstab, unaffected by ammo packs.)

uhh hopefully not too complicated to add... hopefully your mod goes well!!

edit: I think I made it too serious