I mean, do we really need Jupiter as is? Everything Jupiter has done for us with clearing out the trash from the solar system would have been done by a 2nd smaller sun as well.
It's not the solar system's fault that the inhabitants of one of the bodies in the system are bad stewards.
Also, if you have 30% effeciency from the light of one sun, wouldn't the additional light also improve the solar cell since there is now more light to get 30% out of? I mean, more is always better, right?