[@Voltus_Ventus] Here's example. I'll use the_written_John's character because he wrote down his rank-ups.

This is Soldier's skill list from the class description in the first post:
[Skills]
A: 
B:
C: Vigour or Prowess
D: Weapon Proficiency (Any), Armor, Reflex
E: Athletics, Discipline, Awareness

And here's John's Soldier character skills. 

[Skills]

A: 
B: Vigour
C:  Armor
D: Weapon Proficiency (maces and hammers), Reflex, Awareness
E: Athletics, Discipline, 
( Upgraded vigor - C to B, Armor - D to C, Awareness  - E to D)

He picked Vigour in Vigour/Prowess choice, Maces and Hammers in his Weapon Proficiency choice, and then improved Vigour, Armor and Awareness by one rank. 

You can't shift skills to lower ranks in order to gain more rank-ups. You only have 3.