Hmm, you want a ready made Mp3tag action for this special case?
How much time do you want to wait?
In the meantime you can study the Mp3tag Scripting Language and write your own scripting language format string.
A simple first start would be something like this ...
$left(%ARTIST%,2)$upper($mid(%ARTIST%,3,1))$right(%ARTIST%,$sub($len(%ARTIST%),3))
... or ...
$regexp(%ARTIST%,'^(..)(.)(.*)$','$1\u$2$3')
From:
Bread
To:
BrEad
You can set a filter to get only "Mc..." into view.
ARTIST MATCHES "(?-i)^Mc.+$"
Read this thread ...
Case conversion...
DD.20110601.2218.CEST