You'll need a switch. Also, I'd recommend going with a Li-Ion power source over AAA batteries.
However, if your plan is to take the emitter off of the Apprentice LE V5 and put the War Glaive emitter on it, it won't work. The emitter on the Apprentices isn't removable. When you're looking at hilts, the info thing on down the page will tell you if the emitter is removable:
If it doesn't say it has a removable MHS compatible emitter, then the emitter is likely part of the hilt. You can still remove it, of course, but you have to cut it off.