- Audio Cues
One of the clever things WiC did was to give slight personality to the units at your disposal. For example, infantry units told to run across an open field would sound anxious as they complied ("You heard the man, let's move!"), while helicopters' pilots would casually inform you that they had taken out yet another tank ("Scratch one more piece of enemy armor.") This would even crop up in your use of "tactical aid," powers in the form of various air strikes, artillery barrages, and airdropped units: you would hear cheers when they killed enemy units ("Ha! Enemy hostiles destroyed!"), angry shouting when your own units were hit ("Watch it, there are friendlies down there!"), and confusion if nothing was in the area of effect ("Uh, who's giving us these coordinates?").
Now, I don't know if "personality" is exactly what the Overwatch needs from his/her units, but those status updates would be very welcome. There are already a large number of audio clips in HL2's files, so drawing on both Combine soldiers' lines and those from the automated Overwatch voice could easily be used for certain game events: a squad is moving towards an objective ("All units, apply forward pressure."), rebels are within firing range ("Be advised, accomplices operating in area."), a squad is wiped out ("Outbreak, outbreak, outbreak!"), or a unit is idle ("Overwatch, standing by.") That gets the player's attention by keeping him up to date on instantaneous changes in the game, and it provides a slight factor of intimidation for the rebel players: things no longer just seem to happen as Combine rush them, but it instead appears that there is a grand overarching plan going on behind the scenes.
Besides that, I think some manner of noise should be made when the timer for a spawn point, environmental trap, or special unit trap reaches zero. I found a lot of the time that I had to zip back and forth between monitoring the rebels' locations and the various spawn points to make sure I had some way of countering them. It would relieve a little stress from the Overwatch if there was a notice when a spawn point is reset, and I feel like using the dispatcher's voice for this would be appropriate.
- Visual Indicators
Both HUD icons and specific visual effects could help direct the Overwatch's attention to where its most needed. This is the biggest factor behind my desire for an alert when spawn points can be reused: the Overwatch has to keep his/her eye on several parts of the map, both planning ahead for where the rebels will be, keeping track of where they are currently, and spawning and directing units behind the scenes. Audio was the primary method WiC used in relaying info to players, so I don't have as many ideas to draw from there, but there are certain cues common to RTS games in general that would help. A small picture of a Combine soldier on the side of the screen could notify you that a new squad has left the spawn area; a black-and-white picture of a rebel could indicate that one of them has been successfully killed, while one in color could show that one has been revived; a lambda symbol could show that rebels have managed to complete an objective; and perhaps the Combine claw symbol could also be used to represent that a spawn point or trap is ready to be used again. Simple ways like that could go a long way in helping the Overwatch decide what events in the game are worth the most attention and respond accordingly.
The one idea I can draw from World in Conflict relates to the objectives menu. In WiC, there is a long bar at the top of your screen with the flags of the two factions. Each flag takes up exactly half the bar at a game's start, but as one faction begins killing more enemy units and gaining more territory, that faction's flag will expand towards the opposite end. This serves as a general indicator for all players on how well they're doing, with a team that is taking dramatic losses swarming control points in order to stabilize their flag's progress. For the Overwatch player, I'm thinking that a slightly similar idea can be employed: on the objective menu, every objective has a progress bar beneath it to show just how close the rebels are to victory, but ONLY the Overwatch can see this (the rebels typically have numbers and the advantage of being able to choose where to attack on their side, so I think it's less important that they have this). That provides either a sense of confidence, as the rebels are held back and the bars remain low, or panic, as traps fail and each bar shoots up; either way, it can be used as an objective measure on how effective one's plans are.
Also, it occurs to me that some notification when an objective is being captured would be useful, too. The dispatcher's voice would be helpful, but I think a serious alarm that uses visual effects would be welcome, too. Perhaps a klaxon with flashing red lights around the objective to draw attention to it. The Overwatch is alerted to hostile interference, and it suddenly surprises the rebels by showing them it's very obvious to unfriendly Combine what they're doing.
Finally, a small window providing more information on a selected unit would be very helpful. When a shotgun squad and SMG squad stand next to each other, it's nearly impossible to tell which is which without zooming far in. When the player hovers his mouse over a unit, it would be good to have a small window pop up. I'm thinking it should display the unit's current health, weapon, and the number of remaining units in its squad (with the option to select all of said units). This way, you can prioritize which units to send out first at players, keeping heavily damaged units alive somewhat longer by allowing them to attack at range while newer squads close in.
Er. This is considerably more text than I set out to post, but I figure every little bit will help inspire some kind of new idea. Does anybody else have some recommendations or suggestions in this regard?