The undergraduate faculty mail list is running a thread discussing about opening up new fields such as tourism economics, health economics, et cetera. I don't think it is a good idea. Even now they already have too many fields -- and again, it is undergraduate level! What I think is more important is to focus on the core principles of microeconomics and macroeconomics, while introducing math/stat and econometrics as the key tools of analysis and let the students apply them in their senior thesis on whatever topic they are interested in. To harness those interests, they can choose electives: environmental economics, monetary, trade, and so forth. Offering too many specializations in undergraduate econ program is an overkill.
Or worse yet, this is even more likely to happen. My co-author Laura Taylor has a very interesting paper about econ PhD students with weak foundation. I believe what you are taught in undergraduate affects that too (your understanding about economics, while being a PhD student). It is true that you don't have to have an econ undergraduate degree to become a good PhD economist, or economist. But that doesn't mean you can skip your extra homework to understand the basics. And while you're doing that, you might want to set aside many other stuff for a while. You can always get them back later.