There's no problem with changing commanders at half-time just as long as a commander is clearly nominated for a flight, or series of flights, and that commander signs the Tech Log.
I thnk LVO trg/chk training should be given as part of any RHS trg/check.
Sub-charters cost shed-loads and that's my pay rise so, for a limited period, I can go along with this scheme to get over an apparently temp issue............. but my limited support will not be open-ended!