fieldInfo objects are pretty neat but it seems to me they are missing a pretty important method. Currently, you can get field names, assign new names, set visibility, establish split policy, remove fields and return a list of the visible. I noticed you can't set a new field alias though.
If you can set a new name using the setnewname() method, you should also be able to set a new alias using a setnewalias() method. I mean, names and alias' go hand-in-hand.
Without this method, the only alternative to do this in python is to iterate through the fields after export and use the AlterFields tool.