How Crisis On Infinite Earths Can Make Diggle The True Green Lantern
The next Arrowverse crossover is Crisis on Infinite Earths, based on the 1985 DC Comics story of the same name. In the briefest of terms, Crisis on Infinite Earths is an event that sees the Anti-Monitor (an evil inversion of the Monitor) destroying the many Earths of the multiverse until a group of heroes from the remaining Earths rally together to stop him. Famously, the series features some high profile character deaths - including Barry Allen and Supergirl - and ends with the multiverse's many Earths being condensed into one Earth-Prime.
Now, if the Arrowverse version of Crisis on Infinite Earths ends in a similar fashion, then their multiverse would also be condensed into a single universe with only one Earth. This means Supergirl would exist on the same Earth as The Flash and Green Arrow, and the infinite versions of Harrison Wells would be whittled down to just one. Instead of there being a John Diggle on Earth-1 and a John Stewart on Earth-90, there would be only one John Diggle Stewart of Earth-Prime - and that man could be the Arrowverse's Green Lantern. The question that arises from this is, would the current John Diggle be replaced by another version, or will the version of Diggle that fans have come to know and love receive a Green Lantern ring of his own?
What This Could Mean For Arrow's Future
If Crisis on Infinite Earths restructures the Arrowverse just as the original Crisis did for the DC Comics universe, then this crossover event would dramatically change the status quo of the Arrowverse series. And, to be fair, it seems unlikely the CW would want to alter their shared superhero universe quite this much. After all, unlike DC Comics in the 1980s, the Arrowverse isn't so complicated that it needs to be simplified in order for new viewers to sort it all out, though it's on its way to reaching that point.
What's more likely is that the Arrowverse's Crisis on Infinite Earths will include the multiverse being combined or condensed, but only for a short time, similar to how Earth-1's reality was briefly altered during Elseworlds. This way, the crossover can feature something like John Diggle as a Green Lantern without actually committing to such drastic change on Arrow full-time. Even though the Arrowverse contains numerous superheroes and supervillains, many of which have superpowers nowadays, Arrow remains one of the more grounded properties in DC TV's library.
Introducing a Green Lantern ring into the mix would fundamentally alter the show. However, if Oliver Queen can be replaced as the Green Arrow, then there could be an avenue for the show's core characters to "retire" from the forefront and allow a new generation of vigilantes to take over - but that seems to bold for the producers to do at this time. By the end of the crossover, the Arrowverse would more or less be returned to normal, but it would give fans the chance to see Diggle become a Green Lantern - even if only for a short while.