Short-term Commander Improvement Suggestions:
1. Increase limit to how many units a Commander may have assigned to it. 6 seems to be too steep a limit for a freshly-produced commander.
2. Reduce prices of various Command Turrets, especially the higher-tiered ones (which can cost as much as $1750). (May require some tweaks to HP and/or weight to balance out.)
Intermediate-term Commander Improvements Suggestions:
1. Rescale HP of Command Turrets so that each new tier would have HP equal to or greater than the HP bonus provided by the armor upgrade that's required to research them. For example, a Command Turret II would have at least 190% as much HP as a Command Turret I, while a Command Turret IV would have at least 370% as much HP as a Command Turret I. This would help ensure that Commanders remain useful in T2 and T3 games, where turret HP starts to matter less and less due to armor upgrades. (May require reducing the HP of the original Command Turrets to balance out.)
Long-term Commander Suggestions:
1. Allow any units that are assigned to the commander, including artillery, and possibly even repair turrets, to temporarily retreat for repairs, then reassign themselves to the commander once fully repaired.
2. Have any repair units that are assigned to the commander go to retreating units within their group to repair them.
3. Removal of need for Command Relay Center (or any buildings in fact, save for factories of course) to produce them since they don't seem to serve any other purpose. In fact, they'd pretty much be a waste of space.
Features that I hope would NEVER, EVER be implemented:
1. Retain commander experience after death: This would likely cause serious balance issues for commanders. Even if a certain building, such as the Command Relay Center, needed to be present in order for experience to be retained after death, I fear that it would encourage players to send their commanders (possibly only building a single commander), and their accompanying forces, into battle at all times, since all units assigned to the commander would be treated as if their experience level was the same as the commander's.
(I believe that a similar debate was brought up concerning retaining experience upon death.)
2. Having the commander's projectile be treated as an indirect fire unit: Um, hello? Commanders are meant to be leaders of front-line task forces? Even though commanders can have artillery units assigned to them, we already have Sensor Turrets that are better-suited for leading groups of artillery.
3. Increasing projectile damage of commanders to actually make them into a serious threat on their own: When combined with their high HP, I fear that this would make them OP. Also, commanders were designed to be support units 1st and foremost. They need that extra HP more than they need the extra firepower, just so that they could better survive being ganged up on since they'd be such high-priority targets for being able to provide all those experience bonuses in the 1st place.
4. Removing limits to how many units commanders can have assigned to them: Iluvalar provided a nice reason for not implementing this kind of change in the post directly after this one.