I finally figured out how to change the Transmog presets without doing a literal mesh swap. This mod only makes changes within its own suit. For example, it doesn't mean that you can have New Guard's head on Year One's body( a little on that later).

I find the vanilla Transmog presets to be a bit... eclectic... too colorful... so I choose these colors based on their thematic colors, and parts on what I think "protects" them the most, or fits with the theme of the suit better. These were just chosen based on my preferences.

If you're are unhappy with the colors or parts I selected, well, only tools you need are the 3 mentioned below.
If you want to edit the vanilla pak file, I won't link the encryption key here, but you can do a google search for it...

For the curious, the file to edit is in the path Mercury/Content/Systems/Cosmetic/Transmog/Transmog_DataTable.uasset file. That's where it's located in the vanilla pak file. Or alternatively, just edit my file/mod if you don't want to look for the encryption key.

Tools used:
Unreal PAK Tool.zip - credits to crubino, his article kinda led me to this path
UnrealPakViewer
UAssetGUI

Now if you gotten far enough on how to do stuff with these tools, keep in mind that you are editing an index (like an index of an array or list), and indices start at 0. For example if you want color 22, you set it 21, if you want boots 1, you set it to 0. I have pictures that help.

Here's a useful list for the index of a color:
index  0 - Iconic Alpha
index  1 - Iconic Bravo
index  2 - Iconic Charlie
index  3 - Iconic Delta
index  4 - Chroma Blackout
index  5 - Chroma Gray Ghost
index  6 - Chroma Accent
index  7 - Tribute Asylum
index  8 - Uniform Leviathan
index  9 - Uniform Court
index 10 - Uniform Kobra
index 11 - Ultra Cobalt
index 12 - Tribute Atlantis
index 13 - Tribute Slade
index 14 - Chroma Frost
index 15 - Ultra Cosmic
index 16 - Ultra Zurr-EnArrh
index 17 - Ultra Pastel
index 18 - Tribute Drake
index 19 - Tribute Grayson
index 20 - Tribute Todd
index 21 - Tribute Gordon
index 22 - Signal

IMPORTANT - PLEASE READ: You can't pay tribute to yourself! For example, if you're changing colors for Nightwing, you CANNOT use color Tribute Grayson, meaning you can't use 19 when you're dealing with Nightwing's suits. So you'll only ever have 22 colors, even though there's technically 23 colors that exists.

To confirm what suit you're working on, here's another useful list:
Suit01 - New Guard
Suit02 - Titan
Suit03 - Eternal
Suit04 - Year One
Suit05 - Neon Noir
Suit06 - Demon
Suit07 - Privateer
Suit08 - Metal
Suit10 - Beyond
Suit11 - Knight Ops
Suit12 - Shinobi

You'll need to click on "CustomizableKits(3)" and look to the right panel.
P.S. I have no idea what happened to suit09...

Now about the head swap, with permission from deadjack133, I included an optional file where it's his mod, but ONLY the head swap, no other parts swapping. His mod swaps Year One's head02 with Knightwatch's head including other mesh swaps, but I stripped the non-head related things.

Installation:
The usual, extract it to the ~mods folder in Paks. (Make the folder ~mods if it didn't exist in the first place)

Update 1:
I added a stater pack so you can edit right away, so you only need "Unreal Pak Tool" and "UAssetGUI".
1.) Edit Transmog_DataTable.uasset with UAssetGUI

2.) After editing, delete the backup files ending with .bak (doesn't affect the mod in anyway keeping it there, but even if you don't have OCD, it should still bother people having unnecessary files when finalizing a mod)

3.) To make life easier, unzip the "Unreal Pak Tool" to the same folder holding the "myOwnTransmog" folder. So in this folder, it should have 4 things, the folder "myOwnTransmog", UnrealPak.exe, UnrealPak-With-Compression.bat, and UnrealUnpak.bat

4.) Using your favorite file explorer, 'drag and drop' the folder "myOwnTransmog" onto the batch file, UnrealPak-With-Compression.bat

Update 2:
Don't have $300 to shell out for the Collector's Edition? Collector's Edition all sold out? Want the elusive Promethium Transmogs that apparently only comes with Collector's Edition? Save yourself some money/stress. Well... here you go. The new file replaces the New Guard Transmog preset.

Update 3:
I uploaded pictures on how to do the same thing I did for the Promethium and Knightwatch sets since people are asking for extremely specific requests. You can apply the same knowledge to replace any transmog suits. For example, make them all New Guard across all the presets(for online multiplayer immersion??). If you're adventurous, try other characters recipes and apply on someone you shouldn't, like Batgirl's New Guard on Nightwing's New Guard, I haven't tested that, so good luck! If it works(relatively), post your potentially disastrous results in the user pics here or something.