With map sizes bigger and bigger, no longer is the case that a sun or planet MUST take only 1 tile. As we all know, in space stars and planets have mammoth differences in size. Compare our sun to Cephei star or our world to Jupiter for example. It is obvious that those astrophysical bodies have LUDICROUS size differences.

It helps a cosmic game a lot to have those differences more obvious than they currently are.

Of course, it is impossible to implement such size differences by actual proportion. But it is possible to make larger differences than there currently are and make em matter. If it was for pure cosmetics, the modders could just implement various sizes and that is all. However, devs can take some time to make a little "size matters" DLC where the size of those bodies matter more than just looks.

Very large planets could have their own tech to colonize, just like Extreme planet colonization and those late game planets could have notably high class. Very large suns can have their own benefits, like super energy that boosts production. They can be "mined" just like asteroids. 

I do not want to come up with very specific ideas - what benefits there could be for larger astrophysical bodies. My main emphasis is to urge devs make those size differences more apparent than they currently are.