smbakeresq
Explorer
i think that's quite creative, and I would allow it. I would require the roll for each lock.
He is much more creative then us veteran players, basically substituting the spell for every mundane object, even expensive ones like a spyglass. I do let him "get away" with things such 100' of silk rope, since it would fit in a 3 cube, or a bunch of arrows, even though its more than one. I have to careful with "keys" to stuff, if the key to something is a scepter then as DM I cant have a picture of it on the wall tapestry. However it also means I don't have to worry about some stuff, like capturing and disarming the party and restraining them, he can conjure a knife to cut the rope and then conjure weapons to fight their way out.
Even with the Loremaster out and very few summoning spells for conjurers, the conjuration school is great fun to play if you use it well.