I feel like a vocal coach would definitely help. A vocal coach would help anyone regardless of situation, though.
Mike is already a great singer, but he may need to work on his stamina if LP is going to resume touring on a scale anything close to before with him as the only vocalist.
I can see how his confidence may also be an issue, especially knowing that he'll be up there singing songs that Chester used to sing. I just hope he realizes that he IS a good singer, and that he has the full support of the entire fan base behind him.
Personally I would rather him sing the songs he can, and have the crowd sing some of the parts he can't (the bridges of APFMH, Faint, and OSC for example) rather than bring in anyone else just so that they can sing those parts. I think a lot of LP fans would agree with that.