Overused so sounds a bit "blah" imo, sorry - but the benefit of it being so popular means most people know it is pronounced Mee -ah and it is easy to spell.
You could go for less common soundalikes Nia, Gia or Zia (all names in there own right from different origins - Welsh, Italian and Arabic respectively).
Or you could use Mia as a nickname for the perennial classic Maria, or the Shakespearean Marina or Mariana, or even the Austeneque Marianne - all sound more interesting and elegant to me personally than Mia on the BC.