Plungas's experience is definitely limited, he is still a young man. Clark must have great confidence in him if he is to be the DC. Clark obviously knows his abilities well, since Plungas was linebacker coach under Clark as DC. I have no problem with giving a talented young coach a chance, and it is not as if he is being thrown into the deep end to sink or swim, he will have his former DC, now head coach, to continue to guide him.
I also have no problem with Clark keeping some of the old staff, in fact, I think it is refreshing that a new head coach does not see the need to bring in all of his own people as so often is the case. The changes that needed to be made, have been made. The remaining assistants will mostly adapt to Clark's style. If one or two do not, they can be replaced at some later point. I think most of us on this forum believe it is beneficial to keep Coleman and DiMichele. I am not a familiar with some of the others but I don't believe any of them were the problem with the team not winning in the past. Retaining some of the prior staff could be beneficial in retaining some of the current players and with relationships with some potential recruits.
At this point, I just have one thing to say, Go Colonials!