Jet,
Although Krusty seems to be the authority and I will defer to his greater insight, here are a few thoughts.
I think with the recent and significant reduction in overall experience on type within the REX Captaincy ranks the issue of identifying 'supervisory' Captains acceptable to both the regulator and REX to enable the low time Cadets/F/O's to log ICUS at REX could require a serious risk assessment.
Furthermore, the whole notion could indeed be included by the REX negotiating team as forming part of their current EBA negotiations log of claims.
Food for thought...