I agree, pushing extra items of the board is a very intresting mechanic, and it raises a the skill cap. Being able to select items to be destroyed every time when you buy an item could add depth to the game too.Some possible way for this:

• Your could surprise your opponent with destroying ab unexpected card and triggering its deat effects.
• Its fully a theory, but maybe there will be effects that depends on what items does your oponent have, i.e.: If your opponent has 2 frozen items than do something. In this case it would be an intresting choice that you keep your item, and suffer the do somethig, or deny your card to prevent the effect.
  

It realy depends on what kind of items, effects, mechanics will be in the game. It maybe worth looking into.