I was thinking about this as well, the length. How about each Arrowverse show has two eps, all sequential. Arrow, Flash, Legends, Supergirl, then Arrow Flash Legends and Supergirl again with the Supergirl ep the finale. 8 eps total. If Black Lightning is included, 10 eps total, if Batwoman is included, 12 eps total. I think CoIE should be long but not season-long, and I think this would be a good compromise.