Just make the player open their inventory and equip it. No need to make a required client mod. I know from lots of interfacing experience that you need to keep it as simple as possible and not just throw options at the client just because you can. Keep just to the light key. Maybe you can make it so if they use the light key, it auto equips the candle.
okay, I will use flashlight script. But I have problem with emitter, I use script candle light by kaje. somehow it not worked and my candle model was wrong postions. I did posted the link both of them. You can read it.