If they were able to bring Darth Maul back from being cut in half and dropped down a bottomless pit I'm sure they can come up with a way to bring back Mace Windu if they want to.
They could. There's zero reason they should. Maul ended up actually having a pretty great story arc post Phantom Menace. I don't see the same for Mace.
UNLESS....
Clones. Thrawn. I might be OK with that. The way they've set everything up with the trying to clone force users means that when/if Thrawn is the big bad down the line, they could actually pull a LOT from the old EU Thrawn Trilogy. Cloned Mace as the unstable Jedi clone instead of Joruus C'baoth? I could deal with that.