...on the other hand, we're letting Sirius out of prison.
He might not like that as much.
In regards to earlier mentions of destroying all of the Horcruxes at once...it'd probably be easier to skip the Horcruxes. Voldemort's protected from Death, but...well, that's not the only option.
There are plenty of spells for destroying a mind, after all...and also plenty of sealing spells, although most of those aren't perfectly reliable. They'd certainly be good enough to get him out of the way so that we can hunt Horcruxes at our leisure.
Alternatively...does anyone know if there are any Denial-of-Existence spells in accessible media? Because if his root concept is annihilated, that should probably eliminate all of his component Souls as well...
...heh, shame that Exalted isn't out. There is a charm made precisely for attacking all of a being's separate Souls by attacking any single one of them.