This isn't a new unit, but it is something about StarCraft that I'd like to see addressed in #2.
Line Of Sight
At preasent, if your under a tree, damage to your units is reduced, an aparent line of sight going on there.
If your on a hill, you can see farther, and shoot farther, no arguments.
If there is a bunker full of marines, the bunker has to be destroyed first before killing the marines, no argument.
If you have a siege tank on the other side of a wall, and you can't see over it, the enemy travels on the other side, you don't shoot,,, no argument.
You have a science vessel, and can see over the wall, the enemy travels close to the wall,,,,, bang,,,,, no arguments.
A tanks shell should travel in an ark, and kill stuff, over the wall.
When that tank fires at say other marines, they shoot through the wall and kill the tank, now able to see it,,,,ARGUMENT.
Bullets, within reason, travel in a straight line, as should particle weapons.
Just because a shell is lobbed over a wall, doesn't mean you can kill something through a wall.
If you can't do bladed weapons through a wall, you shouldn't be able to shoot through a wall,,,, over and from on top of,,,yes.
Yes this would make a difference on some unit strategies when someone turtles into their base, and doesn't want to come out, especially terran, and zerg.
But imagine the new strategies that would have to be implimented, for offence and defence.