Karax have expensive unit that have average power. He have lots of expensive upgrade compared to other commander, and his talent progression are a bit weak, with the level 7 and 11 talent give direct benefit while leveling him. So my idea of buffing Karax is to combine either buff option 1 or 2 and the universal buff below.
BUFF OPTION 1
The first option is to make unit and Solar Forge upgrade also give extra benefit to building.
Repair Drones. Grant 1 repairing drones to each pylon.
Solar Flare. When Shield Battery restoring shield to friendly unit/building, enemy attacking said unit/building burned for 15 dps over 5s.
Phasing Armor. Make Photon Cannon get 3s Invulnerable time after attacked. 10s cd.
Phase Detonation. Make Photon Cannon attack stun target for 0.5s (0.2s vs Heroic).
Fire Beam. Make Monolith attack burn 30 dps over 5s to target and enemy nearby the target.
Shadow Cannon. Make Monolith attack ignore armor.
BUFF OPTION 2
The second option is making forge and cybernatic core upgrade to also give bonus to building.
Ground Weapon Also give +5 damage (photon cannon), +15 damage (monolith) per level.
Ground Armor Also give structure +1 armor per level.
Air Weapon Also give structure +1 range per level.
Air Armor Also give shield battery +1 target per level. Max 4 target restored at once.
UNIVERSAL BUFF
This buff idea is to make leveling Karax easier by buffing his research, unit and talent. Combine the buff with either the buff option 1 or 2.
All research including Spear of Adun got their cost reduced by 50/50.
All research including Spear of Adun got their research time reduced by 40s.
Unit:
Probe
Also benefitted from Sentinel Reconstruction upgrade and Observer Gravitic booster upgrade.
*This to make probe have more survivability when making forward cannon.
Energizer
+2 damage (8 dps)
+8 damage vs mechanical (16 dps vs mechanical).
Ground Weapon upgrade from +1 to +1/+2 vs mechanical per level.
*Being the only Karax ground unit that able to attack air reliably without ability, this make Energizer Karax option for fighting against Protoss and Terran air combined with it Reclamation ability.
Immortal
Shadow Cannon can be auto-casted to target air unit.
Use Adun Immortal Skin to differentiate from Artanis Immortal.
*Why not?
Talent:
Orbital Assault level 1
New addition: Also give Nexus overcharge after 180s.
Chrono Overload level 5
New addition: Passive. Un-warped Gateway, Robotic Facility, Stargate create unit 50% faster.
Khalai Ingenuity level 11
New addition: Building except Nexus, Assimilator, Gateway, Robotic Facility, and Stargate warp in almost instantly.
Purifier Protocol level 13
New addition: Reduce non-initial Purifier Beam cooldown from 450s to 360s.
Unity Barrier level 15
Reduce cooldown to 180s.
That’s all my idea, I really hope dev will buff Karax somehow.