Which one do you think would be most competitive?
Are there any changes you feel would be beneficial?

Think I would lean more towards the second list. For the first one your deployment and maneuvering is key to make use for Kath ability.. The second list is more straight forward with Boba Fett making use of his ability at range one..

I run something very similar to this and have had good success with it.

================ Ion Kath Scarlet ================

100 points Pilots

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Kath Scarlet (48) Firespray-31 (38), Push the Limit (3), K4 Security Droid (3), Engine Upgrade (4)

Drea Renthal (28) Y-Wing (22), Ion Cannon Turret (5), Unhinged Astromech (1), BTL-A4 Y-Wing (0)

Syndicate Thug (24) Y-Wing (18), Ion Cannon Turret (5), Unhinged Astromech (1), BTL-A4 Y-Wing (0)

Engine upgrades on Kath are amazing as they let you still take green maneuvers and cover a good amount of ground while still getting that free target lock. More importantly however they let you adjust where Kath's re-arc is so that she can fire on targets more reliably

List 1 with the following changes:

-Drop the seismic charges

-Add Ion Cannon & Inertial Dampener to Kath

You get more Ion control and another maneuver option for Kath in the end-game.

Like your ideas, will most likely go with Sierra Romeo Charlie idea. I like the idea of having a good option for the front arc (R3 even more so) and also extra ion can be very useful VS large ships.