Yeah, I think it would be smart to start off with smaller crossovers between shows (like Supergirl in the Superman and Lois show, or the Kate and Kara team-up that everyone thinks needs to happen, etc.) before we try another big show-wide crossover again.
It would definitely justify the Post-Crisis merging of everything and be more feasible production-wise.
About the only thing with Black Lightning is the filming issues since it's not filmed in Vancouver and the cost to ship Cress Williams and his suit is costly, although I think of anyone Grant Gustin would probably be willing to fly to Atlanta for a team-up (he's done it before).