As a general comment, I'm not all that fond of increasing the dependency on various classes. Given that choice of class is an IR, adding incentives to micromanage class composition of an army/realm is not a good idea. We already have enough of a problem with unit choice. Also, we don't want to allow people to min/max the class composition of an army, or create a single "best" class mix.
The idea of adding additional paraphernalia to do additional things is a good one, though. But make sure that you keep your ideas within the scope of the game. A paraphernalia to increase siege engine production in the city, for example, is pretty unrealistic. Things like moving two regions per turn, or transferring gold when outside of cities, are things that just won't happen. Other paraphernalia to reduce the need to return to cities to refit/repair/recruit/etc. is also a very big change that cannot be considered without a rather extensive general discussion about the impact on the game overall. BattleMaster is intentionally structured to limit the range and time-on-target of armies.
Also, adding significant bonuses for various classes, and encouraging a wide variety/mix of classes, will greatly advantage larger realms, at the expanse of smaller realms. Doubly true if the encouraged variety includes a mix of non-combat classes.
Some of the variety and special purpose will be added when Anaris gets a chance to do the War Improvements package. This will allow armies to be special purpose, opening up the possibility of paraphernalia available only to that army.
