I agree that they may feel they're stuck with Biden. I my opinion, if the DNC did decide to pull a switch, they wouldn't replace Biden with Hillary. Hillary is already damaged goods. As you've stated, the Maxwell arrest complicates things further. Biden has already backed himself into a corner by all but guaranteeing that his VP will be a Black female. If Biden is replaced, there will be a huge backlash from Black Democrats if they pick a White replacement. Also, the Bernie Bros will demand that the nomination should now go to Sanders.
“Biden has already backed himself into a corner by all but guaranteeing that his VP will be a Black female.”
I heard there’s a Trump campaign ad out, in Spanish, criticizing Biden for never considering a Hispanic VP — female or male. It could be effective in that demographic.