Mills joins former England manager Glenn Hoddle, FA chairman Greg Dyke, Crewe manager Dario Gradi, Football League chairman Greg Clarke, FA vice-chairman Roger Burden, plus LMA chairman Howard Wilkinson and new PFA chairman Ritchie Humphreys.
That brings the total to eight representatives and Dyke said there would be "no more than 10" in total.
Dyke, who said that it was "a shame" the Premier League had turned down his offer to have a its chairman Anthony Fry on the commission, revealed that Mills had impressed by sending him a paper on his ideas.
Dyke said: "He wrote a very interesting paper and gave it to us - very interesting ideas.
"We are still talking to one or two other people who have not made up their minds."
The commission will report back by the end of March.
Dyke added: "It will take a few months, we are employing some people to work full time on it, to do some research. We have to look at all sorts of other countries, look at the discussion we had this morning, look at Spain, Germany and the rest, look at what they did, what could we do and the rest of it."
Asked about the Premier League's decision, he said: "I spoke to the chairman, who is an old mate of mine, and Richard [Scudamore] and we discussed it before and they said 'look, we will give all the support we can but we don't want to sit on it'.
"I think it's a shame but I understand."
Dyke also refused to discuss England manager Roy Hodgson's future if the team fail to qualify for the World Cup.
He said: "What I don't want to do is get into a discussion about backing or not backing Roy Hodgson at the moment because we have got two important games. I have got a lot of time for Roy Hodgson - I am a Roy Hodgson fan.
"What I don't want to do is get into a debate this week about Roy Hodgson. I think the debate is, 'Are we going to win or not?' I am told we can still lose after Friday night we can still lose on Tuesday if we lose 7-0 to Poland. I am sweating!"
Dyke expressed concerns about England's top flight being a "finishing school" for overseas stars and saying 70 per cent of those starting Premier League matches last season were from overseas.
The FA chairman added: "The truth is we have become a finishing school for the rest of the world at the expense of our own players.
"I care passionately about two things. I want England to win and I do believe that English kids should have the best opportunity to play at the highest level.
"If there are barriers to that either when they are very small because we're not teaching them the right skills or later because they are getting into an academy system where it is quite difficult to get into the first-team, we need to look at what we can do.
"We should sit here and say 'we believe that English kids should have the right, if they have got the talent, to play in the highest level in this country and abroad'."
The Premier League issued a statement last month saying it was committed to engaging with the process. The clubs do not want to have an actual representative however - a move that will give them some distance from any recommendations.
- Sports & Recreation
- Premier League
- Roy Hodgson
- Greg Dyke