All the reasons others have said re: Sean coaching hires. He doesn't have experience outside of the program to make a lot of connections. The nepotism look may scare some hires away. If we hired Venables for example, I would be most interested in his OC hire as that is not his expertise. Wouldn't be worried about defense. With Sean, I would worry about offense and defense but not special teams.
Maybe the biggest thing unsaid in this thread is that Sean isn't particularly qualified for the job anyways. Assembling his staff would be his first major decisions as head coach. Already being on the fence, I would want to see a lot of success there to convince me that he is the best coach for the job and not the coach I fear he is.