I am currently at Lerelace in Galaxy one.
At the moment main planets look like this for me:

After changing the posistion and size of the planet from...
position = "pwm 655444 -3783808 556540";
radius = 18000;
to
position = "pwm 0 0 0";
radius = 3300;
the main planet now looks like this which is much better:

Unfortunately this only works for this planet at Lerelace because it is sized to just slightly overlap the size of the normal main planet.
At least this shows that placing a planet with png textures at the center of the system "pwm 0 0 0" does work.
Now, if only we had an OXP that could read the size of all the planets and then place a png textured planet of the correct size at the center of each system.
That would work.