This is the OFP addon porting really. I've been checking your textures carefully and I think probably just one 2048×2048 file will do for all the tank however, if you decide to do merge them you should do it in steps and not all at the same time since you have two problems, 1 there are away too many texture files and 2 they have many different sizes.

If you decide to merge them I think you should merge them by groups (sizes) first and than in the end join all of them.

Texture Merge tool in O2. 13 separate M4A1 textures into 2 larger textures, 1 is 2048×1024, the other is 2048×2048. They sound large, but from what I've read and heard, it'll better than 13 separate textures.

Basically, you merge all of the textures manually (using Photoshop or whatever), making sure to retain the ^2 dimensions (in my case, with the textures being quite hi-res to begin with, using 2048 and 1024 pixels as my dimensions). Then you have to write a .PTM file, that O2 uses to remap the existing UV Maps, onto the new larger texture.

class inftexmerge {
class object01 {
class items {

class item00000
{
x=0.000000; 
y=0.000000; 
w=512.000000; 
h=256.000000;
scale=0.000000; 
name="SJB_M4TEST\tex\fixorb.pac"; 
angle=0.000000; 
};

class item00001
{
x=0.000000; 
y=0.000000; 
w=512.000000; 
h=256.000000;
scale=0.000000; 
name="SJB_M4TEST\tex\fixorb.pac"; 
angle=0.000000; 
};

class item00002 
{
x=0.000000;
y=256.000000;
w=512.000000;
h=256.000000;
scale=0.000000;
name="SJB_M4TEST\tex\ris.pac";
angle=0.000000;
};

class item00003 
{
x=0.000000;
y=512.000000;
w=512.000000;
h=512.000000;
scale=0.000000;
name="SJB_M4TEST\tex\Stuffed.pac";
angle=0.000000;
};

class item00004 
{
x=512.000000;
y=0.000000;
w=256.000000;
h=512.000000;
scale=0.000000;
name="SJB_M4TEST\tex\30magPolyM4.pac";
angle=0.000000;
};

class item00005 
{
x=512.000000;
y=512.000000;
w=512.000000;
h=512.000000;
scale=0.000000;
name="SJB_M4TEST\tex\right.pac";
angle=0.000000;
};

class item00006 
{
x=1024.000000;
y=0.000000;
w=1024.000000;
h=1024.000000;
scale=0.000000;
name="SJB_M4TEST\tex\ANPEQ2a.pac";
angle=0.000000;
};
};

w=2048.000000; 
h=1024.000000; 
alpha=0.000000; 
file="SJB_M4TEST\tex\M4_Part1.paa";

models[]=
{
"SJB_M4A1_proxy.p3d" 
};
mergedpath="C:\O2_Viewer\SJB_M4TEST\tex"; 
};
};

And

class inftexmerge {
class object01 {
class items {

class item00000
{
x=0.000000; 
y=0.000000; 
w=1024.000000; 
h=512.000000;
scale=0.000000; 
name="SJB_M4TEST\tex\foregrip.pac"; 
angle=0.000000; 
};

class item00001
{
x=1024.000000; 
y=0.000000; 
w=512.000000; 
h=512.000000;
scale=0.000000; 
name="SJB_M4TEST\tex\stuffed2A.pac"; 
angle=0.000000; 
};

class item00002 
{
x=1536.000000;
y=0.000000;
w=512.000000;
h=512.000000;
scale=0.000000;
name="SJB_M4TEST\tex\stuffed2B.pac";
angle=0.000000;
};

class item00003 
{
x=0.000000;
y=512.000000;
w=1024.000000;
h=1024.000000;
scale=0.000000;
name="SJB_M4TEST\tex\regStockM4.pac";
angle=0.000000;
};

class item00004 
{
x=1024.000000;
y=512.000000;
w=1024.000000;
h=1024.000000;
scale=0.000000;
name="SJB_M4TEST\tex\recPolyM4.pac";
angle=0.000000;
};

class item00005 
{
x=0.000000;
y=1536.000000;
w=512.000000;
h=256.000000;
scale=0.000000;
name="SJB_M4TEST\tex\carryPolyM4.pac";
angle=0.000000;
};

class item00006 
{
x=512.000000;
y=1536.000000;
w=512.000000;
h=512.000000;
scale=0.000000;
name="SJB_M4TEST\tex\cranePolyM4.pac";
angle=0.000000;
};

class item00007 
{
x=1024.000000;
y=1536.000000;
w=256.000000;
h=512.000000;
scale=0.000000;
name="SJB_M4TEST\tex\vertPolyM4.pac";
angle=0.000000;
};
};

w=2048.000000; 
h=2048.000000; 
alpha=0.000000; 
file="SJB_M4TEST\tex\M4_Part2.pac";

models[]=
{
"SJB_M4A1_proxy.p3d" 
};
mergedpath="C:\O2_Viewer\SJB_M4TEST\tex"; 
};
};

Those are my two example .PTM files I used.
X = The top left point of the texture (where it starts)
Y = The height of the two left point defined in X
W = How wide the texture is (in pixels)
H = How high it is (again, in pixels)

The above .PTM file stuff is case sensitive.

The normal maps, as well as the cfgmaterials working. edit the values in cfgmaterials to make the 'shine' less intense in most circumstances.

Source Jackal326 in BIS forum topic.