I think the only variegated palm I would consider growing would be a rhapis. All the others look like my queen palm after it gets sun damaged in the spring. I've seen the watermelon palm on ebay and they arent considered variegated, but the color of the new frond (and of the crownshaft) is really beautiful in my opinion!

I disagree totally, if you get a high quality variegated tree it looks beautiful.

Secondly, a 'watermelon' red leaf flamethrower, Chambeyronia macrocarpa var watermelon, is a true variegated tree. Not because of the red leaf that all C.macrocarpa have, but the variegation only show on the trunk of the tree. All the "watermelon flamethrowers" you see on eBay might be seedling from a 'watermelon' mother tree, but very few actually will grow to show the variegation on their trunks.

Yes, that is true, their is some variegation on the trunk of Watermelon palms. Personally, I dont like most variegated palms (I should add licuala to the exceptions and adonidia, and a few others). Since you dont have licuala on your list, I definitely think that is a variegated palm worth looking for, but it would be very hard to grow outside of the tropics.
If they are a very stable variegation with great patterns on the fronds, then it can definitely be a beautiful palm, but they seem to be hard to find and if you do find one, its probably going to be very expensive.
Good luck!
-Alex