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Yes that would be an excellent idea, however it should be limited to 1 large melee/firearm (e.g. swords and rifles) and 1 small melee/firearm
(e.g. knives and pistols).

After a few dozen hours of playing rimworld I have found the combat system to be a little repetitive. All it consists of is hide behind cover and hope
we shoot them before they shoot or get within melee range. Sure there is the occasional flanking but that is only done within out own constructed bases and may allow a couple of extra shots before having to retreat because the opponent is instantly aware of our position no matter what.

Assume we have 5 men capable of fighting and its mid-game meaning we are equipped with a knife, a survival rifle, 2 pistols and a heavy SMG vs 13 pirates equipped with at least 3 assault rifles and a sniper rifle along with the normal weapons. Realistically a full frontal assault would be foolish.A few turrets may help but they can be quite costly if we lack steel or components. So if we can't outgun or outnumber them then we should have to option of outsmarting them using guerilla tactics.

A line of sight system could be added with its features being:

-Colonists can enter stealth mode to reduce the chance of being seen or to hide in shrubbery.
-All entities only have line of sight in a cone in front of them which is seperated into 3 parts:
*At extremely close range(0-2 tiles) targets will be spotted even if they are in stealth mode in a bush as long as they are now behind an opaque       
   object(wall) .
*At medium range(3-10 tiles) targets will be spotted as long as the target is neither in stealth mode in a bush nor behind an opaque object.
*At long range(11-25 tiles) targets will be spotted if they are standing without cover.
-When raiders spot colonist within line of sight they will be alerted and will be less likely to be caught with a sneak attack
-Targets can only be shot if they are within line of sight with the exception of sniper rifles due to the scope.
-If a raider finds an allied body is found dead that raider will be alerted and will attempt to inform his remaining allies if they are unalerted

For a better understanding of the line of sight system have a look at the game:Shadow Tactics-Blade of the shogun which is basically the
same as what I've explained.

Sound system:

-When shot, guns will emit a sound which will alert all raiders within a radius. The size of the radius depends on the gun(a pistol makes less noise
  than a grenade)
-Silencers could be added to certain firearms to reduce radius of noise.
-When alerted raiders will shout to inform their allies. The shout will only work in a certain radius
-If a raider is not killed in the first hit/shot or with a stealth attack he will shout in pain alerting others. Once again the sound only reaches
a certain radius.
-Walking without stealth mode will create noise. Stealth mode will make no sound
-Moving in shrubbery will create noise.

Combat/AI:
--Raiders will slowly encroach on out base while being on the lookout for colonists. For every colonist spotted along the way 2-3 raiders should 
split up from the group to hunt him.With this you could lead those 2-3 raiders into an ambush or pre-layed traps.
-When raiders reach the base a few will stand guard, a few will look for colonists while the rest attempt to break in.This splits them up making it
easier to take them down one by one
-Attacking someone with a melee weapon who is unalerted from the back is a guaranteed kill (if blade)/incapacitation (if blunt)
-Shooting someone in the back has a higher chance to hit.

New stats:
-Perception: The higher it is the further the range to spot enemies in stealth mode
-Stealth : The higher it is the lower the chance of getting spotted by enemies.

Lockpicking (Credit to Ninjakitty66):
-Instead of breaking down doors to enter a base colonists and raiders can attempt to lockpick a door to enter
-Chance of success could depend on the unit's perception and/or manipulation stat
-You can choose to add alarms to certain doors(costing more resources of course) which would trigger on a failed lockpick and alert the base.
-With this you could potentially steal from raiders without getting caught or have to kill anyone.

Fog of war:
I've always found it odd that after crashlanding on a planet we somehow have sight of everything in the area. Hell we can even check what our attackers are bringing to destroy us.
-We will not have vision on anything that isn't within the line of sight of our colonists.
-We can build a radar that needs power. It can detect whether there are animals or people on the entire map(It will not allow us to see what type of
animal,person or gear within their possesion. It needs to be researched
-Friendly colonies will send a message ahead of time stating they will be coming to us within X days. When radars detect people arriving in our
territory within X days players will not know whether or not it is the trade caravan or perhaps a raid.
-When colonies in the early-game do not have a radar it would force players to have a colonist on watch while the others sleep to make sure
they do not get surprised by a raid
               
The ability to take my enemies by surprise is something I've always wanted in Rimworld.

Yes I realize that some of the features I've listed comes with a load of problems:Balance,how well would it work with core game and mod
features, difficulty in implementing it. However I just thought that I'd put the concept here. I apologize for any mistakes I've done in this and
if this topic has already been covered(I am not willing to go through 300 pages of suggestions

Let me know what you think about it, give your suggestions and thoughts on how to balance and implement it into an already in-depth game.

Is this compatible with EPOE and if not any plans of making a patch?(No rush or need to do it cause its already great that its updated to A15)