Hello, I'm a noob with Pkgsrc so take it with a grain of salt:
If I understand you well you want a
ln -s $LOCALBASE/etc /etc/pkg by default. If so:
I use Pkgsrc not on NetBSD and I install it as unpriviledged (and possibly several installations). I have to get into services with Rc.subr, but the take away is that "/etc/*" has meaning of Root for me and I like the clean separation (with a local install and config,) of priviledges emcompassed by these paths.
If this problem can be solved with a symlink, I humbly think it should not be by default and left to the user to add this convenience.
Again this is from a noob, so weight my message as negligeable and probably wrong…