If you’re being specific and limiting your service offering to one thing, you would be wise to aim high. Why? If your business is going to be known for something then you should aim to do the hardest thing better than anyone else.
If your customers see how well you do one of the hardest things – then they’ll likely assume that you can do all the other things just as well. You’ll have the benefit of being highly regarded for doing a difficult thing very well and not have to promote all the other things you know you’re capable of doing. Your prospects will assume that you can do those things just as well.
Having everyone assume you can pretty much do anything – without diluting your message or sales proposition – means you can focus and concentrate on one clear offer. You have distinguished and differentiated yourself by doing the hardest thing better than anyone else – and you have the advantage of your clients and prospects assuming you can do much more.