Well, you can't base spellings purely on whether they look right, but to me, "ageing" does look funny, though I can understand how it might add clarity. If you look at it wrong, it almost looks like you are trying to pronounce it with an "ei" vowel - a-g-ei-n-g - perhaps sounding like "agehng" or "agayng" (hard g)?

Here's one I'd like to know. When someone loses life, they are dying. When someone changes their hair color they are...dyeing?