Most of your fic is ok, it's hard to find any AMG fic at all let alone a
good one.
But...
I take it you haven't read the chapter where Skuld's angel makes her
appearance?
They are not simply "beings" assigned to their dieties. They are quite
literally one with their hosts. You get one by eating an angel egg. Heaven
also appears to be quite casual about selling those eggs too.
You may be familiar with Urd and Bell "splitting" into several mini versions
of themselves, angels appear to be a specialized "split". When dismissed,
they do not "go away" but remerge with their hosts too.
The bond between an angel and his/her host goes deeper than best friends or
even siblings. According to Belldandy her angel is "the closest to me, who
best understands my heart and like a mirror that casts my reflection."
Second, although it appears to be central to the plot, I don't think
Belldandy CAN retire the way you described it. There are hints in the manga
that a god/dess can't lose his/her powers except under the most dire
circumstances.... or you forget to renew your license. That happened to
Belldandy in chapter 106 and she lost her powers for a week. Belldandy says
she tried to avoid using her magic to be close to Keiichi. sometimes she
even thought she could live without it. When it actually happens, she feels
like something is missing. Magic to the dieties is like a limb to us. I
don't think they'd take losing any bit of it too well.
Just thought you might be interested in knowing.
Her children won't occupy her for the rest of eternity too you know. You
have to think in the long term like centuries or so.
Think on those when you rewrite this fic okay? I'll be glad to help anyway I
can.