Well since we know that the Lazarus Pits do exist in the Arrowverse I suppose Nyssa could go do something crazy and revive Sarah who then takes on a new identity... I mean if you have her in the same universe it would be very odd to be a different character.
As far as names go they have a lot of options. They could go with Justice Society, but that may be too close to Justice League for a mainstream show. They could go more obscure with Challengers of the Unknown, or Infinity Inc. but I think they would stay clear of Doom Patrol since that has some possibility on its own down the line. Given the title of the episode where Routh crosses over into the Flash I'd have to guess they will go with All-Star Squadron or All-Stars or something similar.
Or maybe the Brave and the Bold? Do it as a semi-anthology team-up series where they have different stories with various characters teaming up with other notables from around the DC Universe?