Regardless of the load on the engine the charging system has what is called a "break even point", referring to the engine RPM at which there is sufficient output from the alternator to handle all electrical loads. Generally, it's right around 2,200 RPM. This figure drops if the headlight fuse is pulled, though I doubt if it drops to idle speed. Below the break even point the battery has to make up the difference, so if the battery is in a low charge condition removing the headlight fuse is a good idea if you want to hasten the recharge while riding in town.
If it has already been done, it is safe to assume it is possible to do it.
On the other hand, if it has not been done never assume it is impossible to do it.
------- Rob --------