what are the pro's and con's of bringing in a top management person
from another company to head a JIT implementation program. Is there an
advantage of
having one particular person head a JIT implementation program?

Interesting question.  My answer is provided based on my several years
of experience implementing supply chain management/just-in-time
manufacturing-support software at a variety of companies and observing
what factors most strongly influenced success.

First, I believe there is a definite advantage to having a particular
person who has ultimate responsibility for any major initiative.  If
there isn't a single person who is ultimately responsible, then
determining what is happening with the initiative can be very
difficult.  Also, a person whose career is on line to deliver the
project is far more motivated than a group of people for whom the
project is one of many commitments.

However, it is important that the person in charge has real power over
the people who have to change in order to accomplish the project. 
Simply appointing someone is not enough.  They need to be respected
and given the authority to compel action from others.  I have watched
many projects fail because a person was appointed to lead and given no
authority over the operational managers who had to make the changes
for the project to succeed.

Bringing in someone from the outside can be essential if a company
lacks the relevant expertise to implement the project.  However, this
can also be risky in that other people in the company may adopt the
"not invented here" syndrome and actively resist change which they
might otherwise adopt if a familiar person were in charge.  The ideal
approach is to take a respected line manager who has already had
success implementing such a program in his plant or division and
appoint him or her to be in charge of implementing the program
throughout the rest of the company.

Regardless of the leadership approach taken, it is critical that a
consensus be established amongst the senior leaders of the company
before beginning any dramatic project.  Most people find it far easier
to sabotage something than to change, and if managers in critical
positions are determined that something will fail, it almost certainly
will, no matter who is leading the initiative.  Any initiative of this
type is challenging to implement, and the company is unlikely to
succeed unless the managers anticipate and are supportive of
overcoming any short-term difficulties.

I hope you have found my perspective on your question useful.  Please
request clarification if needed.

Sincerely,

Wonko