If we are going to allow Michigan to be included at all in the popular vote tally or the delegate count, it should follow the best metrics available that show where the election would have ended up had all candidates been on the ballot.  Furthermore I believe that any final results should be penalized by 50% in accordance to the rules prior to the rules change that stripped Michigan of it's delegates.  

Fortunately, the exit polls did, in fact ask this question, and here are the results:

http://www.cnn.com/ELECTION/2008/primari es/results/epolls/#val=MIDEM

Vote if All Candidates Were On Ballot Clinton Dodd Gravel Kucinich Uncommitted        
Clinton (46%)                                          97%     0%     0%    0%       3%        
Edwards (12%)                                      30%     2%     0%    11%        57%        
Kucinich   (2%)                                       0%       0%     0%    0%        0%        
Obama (35%)                                        18%     0%     1%    2%         79%        
Richardson (1%)                                     0%     0%       0%    0%       0%        

If we extrapolate the popular vote from this you get:

593837 Total votes * percentage from exit polling

Clinton:    273165.02
Edwards:    71260.44
Kucinich:   11876.74
Obama:      190027.84
Richardson: 5938.37

This what the popular vote tallies should look like if we are being fair about things.  This is obviously a flawed way of doing things but it is far closer than any of the other solutions afforded thus far.

Furthermore we should consider seating delegates with 50% penalty and proportionally indicative of these exit poll numbers that are much closer to showing the will of the electorate than any other.

I cannot speak to how many delegates these would be except to calculate it based upon the percentages mentioned above (we could probably do a county by county breakdown to find out if the elect ability threshold was met in any places for Edwards to get delegates).

156 Delegates/2  * Percentage of votes in the exit poll:

Clinton:    35.88
Edwards:    9.36
Kucinich:   1.56
Obama:      24.96
Richardson: 0.78

For simplicity sake I have left in the candidates that would not have won delegates because they did not meet the 15% threshold.

Employing this method the result would be:

83137.18  Net votes for Clinton
10.92     Net Delegates for Clinton