Unfortunately the very core of the Armoury System prevents that - this is not like FFXI where Job class and weapon were completely separate (and thus a Job could often use multiple types of weapons), in FFXIV's Armoury System your weapon is your class, it's identified by it's weapon or tool. One-handed wands and shields for CNJ/WHM and THM/BLM was a holdover from the original version of FFXIV where shields were actually a seperate sub-class called 'Sentinel' (or SEN for short) - CNJ and THM could equip the SEN class and gain skill points for the class but only GLA could make use of it's abilities.

This changed when 1.0's battle system and classes were redesigned for the introduction of Jobs, SEN as a specific class was scrapped and it's abilities given to GLA/PLD by default, shield use became classless, but THM and CNJ could still equip certain types of shields.

I'm pretty sure Yoshi wanted to move away from single handed wands and shields for THM/BLM and CNJ/WHM (shown by high level THM/BLM and CNJ/WHM weapons being almost solely two-handed) so it's even more telling that SE are rather committed to sticking to the 'one weapon type per class' concept I'm afraid.