lukless Bishop or Normal?

But does that same logic apply for BWs and level 70 wands?

No, elemental mages should still stay lukless. There's no way the minuscule boost you get from wearing luk equips is going to overshadow the 125% damage you could be doing with an elemental wand. If you have enough funding to convert to luk and profit on magic attack, then you have enough funding to buy an ewand, which you should eliminate any reason to go luk.