How is it possible for them to come so close to you and not get revealed? Even at Spy level, it's 5 squares away from detection.

They can see through your disguise when you attack them (shooting people in the face is interpreted as a hostile act).

if you Steal enemy Weapon ( when disguised ) then they wont react, they still gonna act normally like nothing happened

First the bugs I spotted:
Throwing body away while your merc is unconscious removes the body from the sector altogether.

I also think that decapitating terrorists does not work now. It's either that, or zombies mod, or because I haven't talked with Carmen so far?

I can provide savegames to the bugs above.

Now here's a couple of improvements/suggestions to the feature I have

First a small tweak: I think the XML values for enemy clothing prices should be adjusted. $100/$120 for a clothing piece you can get from any soldier is a bit too much, especially at the price Jake buys them. I manually changed the price of each t-shirt and pants to $20, no matter if it's an enemy or a civilian clothing (but that could be adjusted even further, even with the possible question, should NPC buy Deidranna soldier clothing at all?)

Next another small XML tweak: Empty body should take two hands when held in primary hand, IMHO. It's such a big item, than it would be weird to have the possibility to carry two 80kg bodies at once

The next thing that could be really useful, would be making body sprites transparent, just like the living soldiers/mercs are when they are behind the wall - that way you could easily see where is the body of enemy after you killed them near the wall, allowing to easily take his body or clothes.

It would be also nice to have a global option in ctrl+. menu to strip all the clothing from the bodies. (and decapitate and gut options too when we're at it - I think the decapitate one was already discussed on some thread when someone mentioned hiding bodies. Option to mass remove bodies, or at least stockpile it on one spot would be nice indeed, too).

One addition to the clothing system I'd like, but might be hard to implement: instead of making clothing unusable after you shoot the enemy in torso/legs once is to make the clothing more degraded with each successful shot. The more shots your clothing item takes, the more likely are you detected. That would add a bit more realism IMO, avoid confusion when an enemy and it have no clothing (First I didn't knew why, later I've read what was the reason xD) and force your mercs to switch clothing from time to time.

Also, I think it's intentional, since the old T-shirts and the new one behave differently, you can't make rags out of t-shirts obtained from enemy soldiers. It would be cool on one hand, but on other hand it might disrupt the balance a bit, since there's LOTS of shirts lying around if you take clothes from all the soldiers from fight (I like that though xD)

And one last thing - maybe knives should break a little when decapitating and gutting, but not taking clothes away or dragging bodies?

Also, in Omerta where Olga atacks you, there were messages about some missing xml for her.