Hidden Potential

Hidden Potential is a Second Wave option that randomizes stat growth as a soldier is promoted. The range of growth is as follows:

1. Aim:
   • Heavy : 0-2 Aim per level
   • Assault : 1-5 Aim per level
   • Support : 2-6 Aim per level
   • Sniper : 3-9 Aim per level
   • MEC : 1-5 Aim per level
2. HP: Heavy has 60% chance per level of +1 HP, all other classes have 50%
3. Will is treated in the same way as normal, that is:
   • 2-6 growth for all classes
   • 4-12 with the Iron Will upgrade from the Officer Training School
4. Some sources say that the Soldier Movement stat does not increase with leveling, others do. http://wiki.tesnexus.com/index.php/DefaultGameCore.ini_settings_-_XCOM:EU_2012#Soldier/NPC_UNIT_Balance_Mods Says as it pertains to Soldier Moves per promotion with Hidden Potential selected: Heavy has 10% chance of +1 move, all other classes have 20%.
5. My own tests say that Soldier Movement stat does not increase with leveling:

Soldier Class Assault Rank Major with 14 mobility +3 from the worn skeleton suit - shown by number of tiles she can cross: 11 adjacent, or 8 diagonal (we see 7 but the elevation change is one and a half layers, therefore costing at least 1.5 and consuming the last 1). In agreement with https://www.ufopaedia.org/index.php?title=Movement_(EU2012)#Movement_Table%5D

• Classic difficulty
• non born Equal ON - she started with 14 mobility +80 aim
• Hidden potential ON - she started with 4 HP, end with 10
• game wasn't altered in anyway (run done for achievement and to unlock high stakes second wave option)
  

References

DefaultGameCore.ini settings - Nexus Wiki