I tend to agree -
Eireann looks all wrong to me. I want to pronounce it Ire-Ann (Particularly as 'ei' says "eye" in Welsh names like
Eira).
I don't mind
Erin, it's a bit 80s trendy for my tastes but there's nothing wrong with it.
Aran is nms, and couldn't be pronounced the same as
Erin in an Australian accent anyway :-)