I think before I would be convinced he deserves a shot at it he would need to cut the cord at Celtic, go out into the wider football world and gain some more knowledge on different coaching philosophies, styles, tactics etc. get himself a wider education on the game.
When he's done that he should put himself out there for other managerial positions, cut his teeth elsewhere, prove he's got the credentials and earn the right to be considered for the Celtic hotseat.
Howe is also highly rated by all those who have worked with him but just like yourself I'm no entirely convinced of his suitability for the job either, mainly because I don't see the level of experience and know how needed to handle the pressures and expectations that come with managing a club like Celtic.
Kennedy has even less managerial experience and right now I just don't think he's ready for it or has earned it yet. One day maybe but if he got the job now then I reckon it would be wrong for both him and Celtic and fuck up any chance he might have of getting it in the future when he could be better prepared for it.
I know some will disagree with me regarding Howe but they should go have a listen to the likes of Ronny Deila, Lenny and Strachan talk about the immense and unique pressures that come with being Celtic manager, it's a really tough gig and being a good coach is only a part of the job.