If you don't have a hilly commute, a singlespeed can work really well. And, again, if your commute is pretty flat and doesn't involve too many starts and stops, it doesn't really matter whether your bike is heavier than most.

If you want a bike that allows an aerodynamic riding position without being really uncomfortable...

you will have to change the handlebars or get a new bike.

Not such a huge deal though. No bike is easy to pedal into a headwind, except this.