That would be a very bold undertaking on TV, but I would argue that TV is the best place for it, so the story can get the time it deserves. In the end, you could revamp the entire universe, recast if needed, and combine worlds.
Another thing they haven't done much of yet is have more dopplegangers. We've seen a lot of Wells', but how many Barry-Flashes have we seen?
Or multiple Supergirls?
Imagine Powergirl and Kal-L, with the elder Superman being played by Dean Cain? It's almost a shame they cast Cain already.
Or how about a crossover where we have Barry meet the Barry Allen from the 1990 show, played by John Wesley Shipp?