Regardless of the single-league three-division theory, if there are 12 teams, the All-Star Game should be based on "historical significance."

‌20th-century founding teams vs. 21st-century founding teams
There are exactly 6 founding teams from the 20th century
In alphabetical order: Kia, Doosan, Lotte, Samsung, LG, Hanwha (1985)
Therefore
Classic Teams vs. New Millennium Teams
This is how the All-Star Game should be organized.
SSG has participated in the league since 2000
East Division vs. West Division is a poor idea.
Dividing the league into two major leagues like that would ruin the league.
The new millennium founding teams are unpopular clubs.