Jouji Nakata is a great seiyuu, but I'm not sure his voice would fit Saito very well. It's a bit too deep for him.
Personally I'd give it to to the less well known
Ken Narita, since I've always thought his voice sounds very similar to Suzuoki's.
Oh, they'd definitely have to get Mayo Suzukaze to reprise her role. It just wouldn't be Kenshin without her.
And I don't think they'd have any trouble doing it, considering she voiced him again just four years ago for the PS2 game Rurouni Kenshin: Enjou! Kyoto Rinne. Which was even Suzuoki's last work as a seiyuu.