Didn't she have some coaching drama in the past? I know she had a few switches during the 2002 season.
After RG in 2002 she split with Carl Maes who had coached her since way back at VTV, I don't know if the exact reasons for the split ever came out, Maes wanted to spend more time with his family though I think. She then had a temporary coach for Wimbledon Harry something
and then travelled for the US hardcourt events with just her Dad, there is a photo around somewhere of him ballboying for her in Montreal that year
and at the US Open she started with Marc and also Eveline her physio.
I agree with the sentiments above, a coach has to be a friend as well, a confidante, someone Kim could turn to, someone she trusts and have fun with, laugh with and even fight with but then within an hour be chatting again, she has to travel 11 months of the year with them so she has to be comfortable with whoever it is and Kim has known Marc since she was very young at the VTV I still love there first enounter how Kim was throwing her racket at VTV and he sent her from the practice and she wouldn't talk to him after that
Since Kim has started working with Marc, she has won 2 season enders, got to number 1 in both singles and doubles, won her first 2 tier 1 titles, made three grand slam finals, won WImbledon and French Open doubles, which are all things she hadn't acvhieved before, so together they have achieved a lot
I think Marc has tried to work on Kim's game, you can see this year (well at least in the matches I have seen, I haven't seen any since AO) she has tried to come to the net more and finish the points by capatalising on a great grounstroke rather than just start the rally from the base line again. I also think although she always had great courtcoverag, it has improved over the last few years and her slice is better she never used to be able to hit one, and her dropshots have improved - like the one she hit against Myskina in the TB at AO Myskina could only just get to it and Kim hit the winner past Myskina at the net. Her serve is something that is hard to work on cause of her shoulder problem but I think it has got more consistent, and more variety than before, but will always be a problem area. Her forehand is the area that needs work as it can break down under pressure, but they could be working on that we don't know
So yeah to sum up this very long post
I think it wouldn't make a difference cause they could be the best coach in the world but unless Kim gets along with them and trusts them then they aren't going to make a good team and it won't benefit Kim's tennis. Look at Daniela and Harold Solomon they worked a month or so and are now split as Daniela said they just didn't click yet admitted he is a very good coach he had amazing plans in place for her like getting her biomechanically assessed and had determined specific weaknesses and technical problems he was going to work on, but Daniela is back working with Nigel Sears as she trusts him. Unless the player trusts the coach they aren't going to do what the coach says.