Surrounding your keep with towers is not an anti-3 star base.
at high levels, almost any competent base will not be 100 percented.
It's a good strategy, but can still be defeated.
For instance, if a Conrad-Ram rush were to have rams attack different towers, it would be very easy, as the rams would not need to travel a great distance to get to the next tower once they are done destroying one.
Also, Alexander Nevsky would have a field day, as his fire would hit quite a few towers in one hit (with his ability)
And of course, Winrich.
But anyways, yes, this would work. it's just not a guaranteed 100 percent defense