That's a good list. Might also think about various combinations, like thickening the harmonies and/or the BGVs.

Another good "coloring" for vocals is a slight delay, which can be panned with or separate from the vocal. I almost always pan harmonies (at least slightly), too.

Waves' Abbey Road Automated Double Track is another simple solution for thickening, though it won't make you sound exactly like the Beatles.

Used to use a lot of shortcuts like Melodyne to create doubled tracks or harmony lines, but now I just go ahead and sing everything. Doesn't really take much more time (if any) and I like the results much better. I'll use composite vocals for all vocal parts to compensate for my lack of, uhm...precision.

As important as vocal arrangements are, and they are one of my favorite things to do, how they fit with the backing track arrangement is just as important. So carving out space (ie stereo image) and/or bandwidth (ie EQ) is necessary. Like a lot of you, I'll leave lead vocals, stereo drums and bass centered and distribute everything around left and right. I'll probably use a high pass filter on a harmony or BGV bus since I don't need those frequencies. I'll probably compress the BGVs a bit so they sit in the mix better.

The list goes on...

DC Ron
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Too many guitars (is that a thing?)