How to make pro players use every available structure/unit?
Just pretend that its mounted on the wall (having only its barrel sticking out of it), then it makes sense. If it would be too complicated to program which wall to let which shot through allow enemy turrets to shoot through enemy walls as well; it's not too often such a situation happens anyway. Can't get stuck on details, infantry can see and shoot over cliffs after all so allowing the turret to shoot through walls shouldn't be a problem.
How about renaming "Turret" to "Ballistic Turret" or "Cannon Turret" btw, since "Turret" can mean any type of turret. When I hear "turret" I primarily think of machine-gun turrets myself.
Why is it rarely (almost never) built?
+ If you have credits, you spend them. Your build queue is never empty so you don't hoard credits.
+ Ore Refinery provides enough ore capacity.
What would maybe make it more worth building them for pros?
+ Nerf Ore Refinery from 2000 capacity to just 750. (2k is a huge amount, especially when pros never has just one Ore Refinery.)
+ Increase Silo from 1500 capacity to 2000.
+ How about rewarding not spending credits? When no credits are being drained the silos can process stored ore. Gain 1% of X per silo every second you don't build anything. X = amount of credits above the combined capacity of all Ore Refineries. Example: You have 2 Ore Refineries, 3 Silos and 2500 credits. You'd get 3% of 1000 credits every second you are not building units/structures (after 1 sec you have 2530 credits, 2 sec 2561 credits, then 2593 credits and so forth).
This would open up a new playstyle that makes it worth while to not spend your credits for a while in order to gain a bunch of extra credits passively over time. It would also allow for strategic plays where it's worth while to destroy the other players Silos.
Btw consider renaming "Silo" to "Ore Silo" since a "Missile Silo" isn't a subtype of "Silo".
Sidenote: I've noticed 1 Ore Refinery doesn't equal 2000 max credits, more like max 5000 credits? So it seems like you are allowed to have 3000 credits without any Silo or Refinery? If true that default amount would probably also need to be lowered in order to make Silo viable.
+ Make civilians auto-escape being runned over if possible. They should never get run over as long as they can panic into some direction.
+ If next to a tree the civilian would become cloaked, only discoverable by enemy Dogs. This means Civilians could just stand around next to trees, giving a bit of vision to the player.
+ Finally civilians should be able to enter all Civilian structures. This gives the player 25 credits and removes the civilian from the game. More importantly, the player also gains 8 cells of vision of the civilian structure.
So in short: The purpose of Civilians would be to give sneaky vision. Vision is lost if the civilian structure is destroyed by the enemy, however this always leavs a permanent ruin. Walk another civilian into the destroyed structure and it becomes repaired, granting vision once again.
The enemy player can search houses with a guard dog (giving dogs a new purpose) and if found the vision is lost over the civilian building and instead the enemy player gets vision of a random enemy building for 10 seconds (same area of vision as if a spy plane flew over the enemy building).
You can't enter a house that an enemy player already have a civilian inside. It just won't go inside (making the player aware that it's occupied so he can destroy it or send a dog).
I would love for all airstrikes/parachutes/bombs specials to be based upon two clicks: The first second click sets the actual target of the planes and the first click is used to determine the angle the planes fly (simply draw a line from the first click to the second, that's the flight path and direction the planes should come in from).
If the engine doesn't allow for this I would rather have the planes always take the shortest possible path, from the closest edge of the map to the target.
This is probably the suggestion I would rank as most urgent among my ideas. It breaks my heart every time I see a perfect bomb spot ruined by bad plane angle (either the planes take too long to arrive, gets shot down or just miss their mark, all due to pure chance). It's not a minor randomization to spice up the game, it feels like a dice roll.
In the original game you would instantly orient yourself as soon as you saw the straight edges of the map. "Oh okay, I'm in the top right corner of the map." Many, myself included, don't think about looking where I spawn before starting the game, we rely on the map edges to see where we are. Straight edges would help to identify these bounds immediately. It might seem like a small deal but reducing annoyance for new players is key if you want to keep them around.
Shrouded non-straight edges also gives an unfair advantage to some players because it helps hiding units at the edge of the map. I wouldn't consider this a feature, more like an exploit. It's unfair that the bottom player can sneak in helicopters into the top player's base simply because he can hide them outside of what's being rendered.
Why is it rarely built?
+ You don't have much cash left over unless playing a dedicated support role.
+ When playing 1v1 they are useless since you have no team mate to give money to.
What would maybe make it more worth building them for pros?
+ Make them able to enter ore mines.
+ Doing so would immediately spawns 8 cells of full ore around the mine.
Can be used to sustain late-game economy. Shouldn't be as powerful as it sounds since they cost 500 to build (that's 1.5 cells of ore if I'm correct) and unless all cells around the mine are completely empty you don't get the full 8 cells value out of it. Requires some micro to pull this off, especially while a fight is going on.
If my civilian idea above is implemented you could send a supply truck to a civilian house occupied by one of your civilians and that would increase the line-of-sight from that structure by 4 cells (can be done several times). Sounds whacky but would be fun to see if a player finds it worth to do so in some match. 1 civ + 1000 credits for 16 cells of vision. Plus a lot of dedication to doing it without the enemy noticing.
Same if you can mark a building as primary (Barracks/War Factory), make both left double-click and right click work.
Can't deploy something or mark it as "primary"? Then make left double-click power down or power up a building (a shortcut so you don't have to use the "lightning bolt icon"). Spares newbies from remembering keyboard shortcuts (which I believe is X? X should be restored as default for "scatter move units", as it was in the original game. The current Ctrl+X key combo doesn't feels comfortable for scattering units).
Making it more comfortable to transfer your strategic thoughts from your brain into the game is always a plus, requiring people to spend as little time as possible learning controls/interface is a sign of a great game! Giving people options to control the game they want to control it leaves more energy over for strategy decisions, right?
It would be a good way for players to immediately see where they are on the map and how big the map is. Especially helpful for new players who haven't played the map before. Completely new players to the game would understand that there is a mini-map option as well, just that it isn't activated yet, and they would see where it will be later.
Many new players go a little nuts from hearing these lines all the time. Can add an option to set the cooldown duration if somebody want to return it to the old 0 sec cooldown (a few will probably increase it to maybe 6 sec).