A magus with this magus arcana
must select one other class that grants the ability to
cast spells. The magus can use his spellstrike and spell
combat abilities while casting or using spells from
the spell list of that class. This does not allow him to
cast arcane spells from that class’s spell list without
suffering the normal chances of arcane spell failure.
The magus must be at least 6th level before selecting
A magus with this magus arcana can activate a wand or staff in place of casting a spell when using spell combat.
So, if a Magus takes both these arcana (choosing Wizard for Broad Study), but doesn't multi-class, can he/she/it then use wands with any wizard spell during spell combat?
Ok I like this, it's a neat idea but I think you've made it more complicated than it needs to be:
Wand Wielder states, "A magus with this magus arcana can activate a wand or staff in place of casting a spell when using spell combat"
It doesn't say, "A wand or staff with a spell from his spell list on it."
So all you need to do is make the UMD check and have wand wielder and then it doesn't matter what spell you have in the wand/staff.
Basically: You don't need broad study to do this -- in fact broad study won't help at all since it doesn't actually give you a spell list (just the ability to use another class's spell list with spell combat) -- without that list you can't use the wand/staff without a UMD check. Hence Broad Study is useless for what you want to do.
My reading and understanding is that it gives access to the spells for use with spellstrike or spell combat but doesn't grant the list. You must mutliclass in order to use the feature -- or have spell storing devices (like rings of spell storing for example).
It is one of the few abilities they have on the magus I really don't like -- seems better suit to a prestige class to me honestly. Any such combination of two classes is almost going to require one anyways, and the mystic theurge simply will not cut it in this case.
If you're right (and I concede that you probably are), then I just don't get Broad Study. You can't take it until 6th level, and it's only useful for spell casting classes, which suffer the most from multi-classing. What kind of build would utilize it? At 7th level, you'd gain the ability to cast 1st level spells of the new class. That's...underwhelming. I just don't see it.
Edit: I guess one could take a single level in a spellcasting class for access to the spell list, so that wand wielder would apply for any spell on that list, but, as you pointed out, that can be done with UMD and without losing a level in Magus.