Higher level equipment usually yields better resistances, skills, and added effects. You can exploit the game's method of determining a officer's level by increasing the number of "pertinent" skills by changing the officer/leader's troop job into a job that has multiple skills. The sum of those skills will determine your leader's level. Once you assign that leader as an officer to your leader's unit, the officer retains his or her level, despite being in an infantry unit (i.e., the units under Gerald, Lucretia, Kendal, or Regnier).

Keep in mind that any high level equipment will be de-equipped if the leader's level suddenly drops because of a troop job change (hence the game message). This hint is more applicable for Kendal and Regnier, as their campaigns allow you to freely assign other troop leaders as personal officers.