Absolutely fair, no munchkinism!
Even better would be to replace those "charged items" with spells. Several of those listed can, in fact, be cast spontaneously without fatigue (and thus without any risk of botching) by a magus of some experience. Even those that cannot, can be easily learnt as formulaic spells with "leftover" points from other spell research.
And for a circular structure (and/or rooms, objects etc.) consider the possibility of replacing the "mallet" with a D:Ring Maintain the Demanding Spell, learnt as a formulaic. It's used in extensively in our sagas. Some examples of what can accomplished - and the savings for a thrifty covenant - can be found here. You are encouraged to add your own (remember to provide not only the spell, but a rough analysis of how much you'd expect in savings)!