I caught that and it was pretty cool written, only downside is that it kind of strongly hinted the whole team would be coming.
Very true, but the downside is out of character behavior or alternate reality versions. Going the original route saves you from having to explain weird behavior from the fanfic character or annoy readers when characters does weird stuff.
I think what is fitting depends very much on the story. Like you should not fight your muses, but to follow them...if staying with the flashfic format makes you more productive then do that.