My wife has an Electra Deluxe Relic that she loves. We recently moved to a more hilly city where getting around via bicycle is more feasible than before. The problem is that the Shimano Nexus 3 speed does not give her the gear range suitable for where we live. The low gear is not low enough and there is quite the jump between the 3 speeds. I am looking into getting a used Nexus 7 speed hub. Is there anything else I need to look into such as spoke length for the wheel? Also how much more will the weight penalty be?

I know a nearly 50lb beach cruiser is not ideal as a errand runner/grocery getter etc., but she loves the bike too much and gets way too many compliments on it for her to want to replace it.