The fact that Aventine has an experimental slipstream would make for some interesting stories. But I still don't buy the idea of Ezri making captain so fast even she is the ninth incarnation of Dax.
I take it, then, that you also don't buy that Picard would have assumed command of the Stargazer?
(Seriously, Picard's taking command of the Stargazer and Ezri's taking command of the Aventine happened under almost identical circumstances: Captain and first officer killed in battle, forcing the late-twenties second officer to assume command. The only difference is that Picard was 27 and Dax is 26.)