Okay. Here's my tutorial on how to hack in hair to ME1 using hex modding. It's not the most straightforward process, but very do-able with some patience. ALWAYS backup your saves.
What is hex modding? In general terms, it's basically opening up a save file and changing the raw data using a hex editor.
I use 2 programs to hex mod:
1. First step is finding the save file you want to edit and making a copy so you have a backup in case things go horribly wrong.
I use a Shep that has the "classy" hairstyle to start, because it prevents any clipping issues that might occur with the buns, and because the mesh name makes the hex data easier to edit to the new meshes.
Copy your save file somewhere. I use the desktop.
2. Next step is to extract the save data using 7zip. Drag and drop your save file over to the 7zip.exe
A window will open up with 3 files: player.sav, state.sav, and WorldSavePackage.sav
We will be editing player.sav
Extract all 3 to a folder by highlighting the files and hitting the extract button. Navigate to a folder you want them extracted to, I created one on the desktop named "ME1 save edit" and hit OK.
3. Now go to the folder with your 3 files, it's time to hex edit. Open up player.sav in HxD.
It will look like this:
Make sure you're editing using insert, you don't want to change the length of the file.
The first entry we need to edit is somewhere around offset 2735, noted at the bottom. If you know the name of your current hairstyle, in this case the "classy" you can find it using the search function.
Replace it with the desired hair name. In the example, I'm changing it to the "Cute" which is Dr.Chakwas' hair. Changes will be highlighted in red. If there are letters left over, as in this case since "Cute" is shorter than "classy" replace the remaining letters with zeroes.
Next place we want to edit is somewhere around offset 3670. It may vary depending on your save file, you might have to search a bit for the hair meshes. If you're familiar at all with Gibbed hair editing, the strings are largely the same.
We start with "HMF_HIR_Cls_Diff" and change all the "Cls" to "Cte"
Save your file and close.
4. Go back into 7zip and navigate to the folder with our 3 extracted and now edited files.
Highlight the 3 files, excluding the backup, and hit the "Add" button at the top to recompress it. Make sure it is in zip format. If you go to your "ME1 save edit" folder you'll see a zip file.
Rename it to the name of the original save you are replacing, making sure to edit the file type. You might need to go into your windows preferences to display file type in your folders.
5. Open the new mass effect save you just created and the original in HxD. You'll need to copy the first 2027 (8231 in decimal) bytes from the old file to the start of the new one to make it a valid MassEffectSave file. Don't replace anything, just add it to the very beginning.
6. Save and close. Drag and drop your new save file into your Mass Effect saves folder and you should have a new hairstyle when you load up the game.
The process works the same for male Shepard. I've only tested it with the Mohawk hairstyle.
Male Mohawk, original hair was "FormalSpikes"