Raise the custom css character limit to something higher than 20000. This will allow for more advanced and better looking Kagi themes. Nothing will change unless you are developing a theme for Kagi.
People will be able to write better, more advanced themes without being limited by character limit.
Other applications often have no limits, and will not sync the theme to the account. By handling themes locally, there will be less stress on Kagi's servers (if that is a problem).