Whats wrong with saying there are more type 1a supernovas than we expect simply because of incomplete data in our standard models. I find that a pretty easy admission since there are many problems we are currently working on that might have an impact on these. As in does the amount of dark matter change with time, has the CC varied with time. Is the fine structure constant equal in all areas of space.... we can go on and on I think its likely as more data comes in we will know why there are more than we expect.
Just like until dark matter we couldn't tell you why our galaxies didn't fly apart.
The fine structure constant has been proven not to be equal in all parts of the universe, so you can scrap that one.