This enables the "Cheat Vest" item for purchase from the start of the game.

Default is to only give 1 armor, but the XComCheatVest.ini can be modified to give far more.

For stats, it can give additional -

• HP
• Armor (Fixed in v1.1)
• Mobility
• Aim
• Hacking
• Defense
• Dodge
• Shield (v1.1)
• HP Regeneration (v1.1)
  

It can also give additional abilities normally only found in other items or armor.

These include -

• Mindshield
• Grapple
• Wraith
• Fortress
• Squadsight
• Shadowstep
• Teleport (v1.1)
  

Cost of vest can also be modified in the ini (v1.1).

Changes to the XComCheatVest.ini take effect on the next load in the strategy map.

The location of the XComCheatVest.ini should be - SteamApps\common\XCOM 2\XComGame\Mods\CheatVest\Config 

If you save the game in tactical then changes will not take effect until the end of the mission
and the strategy map loads again. Previous ini settings will apply to the save.

This was mainly done as a way for me to learn my way around the developer tools.
Things such as reading from an ini file, adding abilities and items, etc.

I may add more to it in the future if there is any demand, or I want to learn other parts of the game.
Thinking about adding critical chance, critical damage, damage modifiers, etc.

Source is included.