I can't see anything other than Icadets upgraded as normal when their turn comes around. The Icadet T's and C's are to lower the cost base of the tech crew group, unless DEFO's are hired on the same contract (or less!) i can't see the reasoning to go and pay more for someone else. The quicker CX upgrades Icadets to FO and CPT the lower the cost base will be.
Can any current Icadet confirm that the 'forgivable loan' is pro rata?