This is not a bad idea. Fred Thompson would bring presence and conservative credibility to the ticket. His age could be a problem, however.
This is what I wrote earlier today about McCain’s VP pick:
Ive been saying for months now that Governors Tim Pawlenty of MN and Mark Sanford of SC would be the two best choices for McCains runningmate (I also mentioned Congressman Mike Pence of Indiana, but McCain probably wants someone with executive experience); while I supported Fred Thompson for President, and think he would also make a great VP, I think McCain needs to find someone younger (and name Fred as Attorney General).
As for those who believe that Pawlenty isnt conservative enough to be McCains runningmate, they should keep in mind that Pawlenty is as solidly conservative on right-to-life, RKBA and immigration as they come, and that he was able to be reelected in Minnesota despite the states Democrat lean and the horrible political environment for Republicans in 2006. I believe that John McCain will be able to carry Minnesota (48% for President Bush in 2004) and Wisconsin (49% for Bush) with Tim Pawlenty on the ticket, and that Pawlentys blue-collar background will help McCain carry Michigan, Ohio and Pennsylvania to ensure a large Electoral College majority.