Every commander has a select few units and it is completely valid to limit the player on building all units as commanders need to complement eachother.
However, I have often asked myself. What if some units were added to certain Commanders. With the ability to replay commanders from 1-15 again, I sometimes wished some commanders got some of the units that it has baseline in Melee Mode too.
Given that recently some new difficulties were added and the AI overall has been improved how about this:
Raynor:
I think Raynor would be very well served with at least 1 spellcaster. It’s completely lacking in this department.
Ghosts would be my choice given that Raynor is very heavy on Infantry.
Kerrigan:
Kerrigan is okay generally and heavily reliant on her Hero Unit, but a spellcaster wouldn’t be out of place either. Adding in an Infestor or Roach would be lovely
Artanis:
In general it’s a shame how he lacks a Sentry. I think adding in the Sentry fills in the Gateway as a standard Melee Protoss nicely.
It would also be nice to give Shield battery to Artanis, given how it’s become a standard defense structure for Protoss in Melee.
Swann:
Swann could really use another aircraft. The Viking would in my opinion be the perfect mech unit added to his starport, given that it can switch between ground mech and air mech.
Zagara:
A commander with very few units and they are all generally low tech and throwaway. Perhaps granting Zagara Hydralisks or Infestors with infested terrans would be nice.
Vorazun:
Similar to Artanis, giving Vorazun a sentry (while not really part of the Nerazim theme) would add to the Gateway. Other options could be to add the Robotics Bay and allow Dark Templar to build Annihilators, though this might make it too much like Zeratul
Karax:
In my opinion, Karax primarily lacks a Stalker-equivalent. Giving him a Campaign adept with air attacks or a stalker or dragoon would be nice
Abathur:
Abathur has one of the best unit options and I find it hard to come up with something for him
Alarak:
Giving Alarak the Taldarim Bloodhunter from the Campaign would be really cool given that Alarak has it’s air disabled, so not having a Dark Templar equivalent is kinda weird.
Nova:
For me, playing Nova I generally rely a lot on the Raven, it’s healing and damage potential is very useful. But perhaps Nova could receive early game Medic Squad to help out and keep early Marines alive.
Stukov:
How the heck does Stukov not have Infestors? It’s the infested Terran race. Let’s fix it.
Fenix:
Giving Fenix a Warp-Prism and Shield Battery would nicely fill in his needs, then his sentry can be given Shield Recover or Forcefield.
All commanders afterwards are harder to say what they should get because they already have quite a few units, more than the old commanders generally got.