Just to be adversarial, how do you know the sun is massive (e.g. in mass, not volume)? Is it not based on a series of suppositions, including heliocentrism?
How do we know how massive the Sun is? Well we know how distant it is by direct measurement. Based upon its apparent size and its distance we can calculate its real size (volume). As far as its mass, it is made up mostly of the two lightest elements known, so any change to that will only make it more massive.
Moreover there is a minimum size for a star, otherwise its gravity will not be sufficient for nuclear fusion.
How small do you need the Sun to be for it to circle the Earth? Care to make a calculation? How would your ‘mini star’ undergo nuclear fusion? Why does it look so big and why is it measured to be so distant?
One needs to discount all Science, reason, and measurement if they wish to make the Sun small enough to circle the Earth.