You've only got to go back twenty-odd years to see grids at the TT with well over 100 entries. I don't see why there can't be a reserve list of sorts. There will always be no-shows and non-starters, so if 90 are theoretically allowed to start and you have 15 non-starters, then let the resrves fill the remainder of the grid as long as they've achieved the qualifying time.

This will bring more interest into practice week (which it needs...) and ensure full grids for race week.