I'm potentially interested, but…
I prefer the suit to be for Bitcoin asset value.  That's global, so presumably the customer base is bigger.  Also, the jurisdiction can be chosen to be the one most favorable to true class action suits.  Finally, we could choose a jurisdiction with good KYC and AML, for an expectation of identifying the perps who actually stole the assets (if that's what happened).  Also, BTC was key to the crime, whether it was theft from the exchange or the exchange perpetrating a fraud.
I'm sure there were lots of BTC-only victims, due to the low prices at the end and the resulting arbitrage opportunity.
Perhaps we need N+1 separate suits, for N Fiats plus BTC, but let's focus on BTC first.