So the lineup I am currently using is this one:

This lineup works great for my current power and will stop most teams in their tracks if used correctly. It's highlights are blindness/acupuncture chase, beefy shield, moderate chance of Itachi using his 30 high-combo chase (causes 4 ignition).

However in order to make my team stronger, Iruka can be replaced a various ninjas that have similar abilities (interrupt) which is what I needed help with... The criteria that I made was that the ninja has to be able to interupt in some way (via interrupt/acupuncture/immobile etc) Also bonus points if it can: Chase high combo (to help increase chance of Itachi chase), use its mystery first turn, is a Uchiha ninja.

That being said, here are 6 ninjas who I think would work well with my team. *Note I haven't personally tested any of these teams in actual battle.

Here's the breakdown of each team:
Iruka --> Shisui

Requires: Serpent and Shisui

Adds: 40% barrier buff, Chaos chance, Lots of ignition, Tag chase, Dodge chance, Double attack(2-4 hit)/Cleared Debuffs (Itachi passive)

Removes: 30% Konoha buff, First turn interrupt, loss of shield, high combo chase

Approx Cost: 12k-16k Coupons

Iruka --> Masked Man

Requires: Serpent and Masked Man

Adds: Immobile + Buff loss Mystery, Double attack(2-6 hit)/Cleared Debuffs (Itachi passive), Immobile Chase, Dodge Chance

Removes: 30% Konoha Buff, loss of shield, high combo chase

Approx Cost: 12k-14k Coupons

Iruka --> Kakuzu [Earth Grudge Fear]

Requires: Kakuzu [Earth Grudge Fear]

Adds: Interrupt/Unique Mystery, Better standard (1-3 hit), high combo chase, Super Armor/Clear debuff

Removes: 30% Konoha Buff, loss of shield, first turn interrupt... (Maybe? Not sure)

Approx Cost: (Est. I have no idea) 10k-15k Coupons

Iruka --> Minato [Jonin]

Requires: Minato [Jonin]

Adds: Dual Interrupt/Tag Mystery, Double Chase skill + Scaling Passive, Dodge Chance

Removes: 30% Konoha Buff and loss of shield

Approx Cost: 13k-15k Coupons

Iruka --> Minato [4th Hokage]

Requires: Luck

Adds: Mass Interrupt/Tag + knockdown Mystery, Op Attack + Flying Raijin Slash, 40% Res buff, Dodge Chance

Removes: First turn Interrupt, 30% Konoha Buff, loss of shield

Approx Cost: 20-100k Coupons (20 btw not 20k)

Iruka --> Tobirama [Edo Tensei]

Requires: Tobirama [Edo Tensei]

Adds: Quick Refresh Interrupt/Tag, Strong Standard attack (1-3 hit), Insane Scaling, Dodge Chance

Removes: 30% Konoha buff, loss of shield

Approx Cost: 15k-30k Unstable prices

Tl;dr: I need help on which ninja I should buy, I currently have 8k Coupons stored up and I'm f2p, I'm leaning towards Masked Man/Shisui/Tobirama (In that order) If theres any other ninjas that you think would work well, please share :D Thanks!