1) I still haven't read the FAQ, I am sorry for this, when I get time I will try, but I wanted to at least respond to what has been said in the meantime. I appreciate it may mean people having to offer answers already in the FAQ, and I am sorry.
Don't worry about it. I do strongly reccomend reading the entire section on Ultimecia there, because it will save us a lot of time, but please don't feel any need to rush. It is admittedly rather long after all =P

Okay, this is just my stance, so if you don't find it agreeable, then fair enough. Basically no I don't think it matters what the writers intended (if they intended anything at all), it matters more what FFVIII the product indicates. If the question was "What did the writers intend?", then I would, based on Ultimania, say either nothing, or R=/=U. However if the question is "Based on the evidence presented in FFVIII the game, how strong/appealing is the possibility of R=U?", then this is a whole different ball game, is one that CAN be logically debated, and in my opinion is a worthwhile question.
Well, I can appreciate that stance, even though I usually concentrate more on finding the intention of the writers when I analyse these things. Now, I agree that the issue can be logically debated and that it is certainly worthwhile, but I don't think the R=U is strong or appealing based entirely on the actual ingame facts either. The FAQ will demonstrate why, I suppose.

Also, given the way aisle_s described how the characters and story were created, I feel we may be better off using my method rather than appealing to the artistic integrity and vision of the writers methods
Perhaps. It's certainly arguable, but I feel that either way the theory falls short, so I guess it doesn't really matter to me that much.

Well, you may be correct here. I'm not confident on how and when it is presented in the Japanese version, or how well it is translated.
I suppose that's understandable. My translation here was given by a GameFAQs user a long time ago, and it's obviously impossible to really know the extent of its validity, but I think we can safely assume that it expresses the general points.

However, I would not dismiss my problem with the word 'feel' as semantics. If the specific word summon was changed, then the statement would not obviously point to Griever at all, so the strength of that word in supporting one version, seems to carry only equal weight as 'feel' does in debunking that version.
This could be argued back and forth I suppose, but in the end, Ultimecia says she will summon something from Squall, and she then summons Griever. It would be absurd to think that her threat of summoning "the most powerful of things" from Squall is in fact entirely unrelated to her summoning of Griever straight afterwards, when you consider that Squall has previously said that Griever is known for his "great strength". That would make no sense at all:

Ultimecia: "Hey Squall, I will now summon something very powerful from you and have you face it in battle.

*summons Griever*

Squall: "Oh noes, you summoned the creature I consider to be very powerful and strong! Your threat was not empty!"

Ultimecia: "Foolish SeeD, Griever came from somewhere entirely different lolz"

I just don't see it happening =P Merely calling it an "idle threat" still goes entirely against the fact that she summons Griever straight afterwards, and the loneliness Squall faces is due to TC and not Ultimecia, who iactually dies before Squall goes to that desert place. There simply MUST be a direct correlation between her threat and Griever. Her threat is like a gun, and Griever a bullet. The logical suggestion is that she actually fired the gun, but you are suggesting an entirely different gun was used.

I just don’t see why Ultimecia would do it, or why Squall would be intimidated by Griever, or how the Griever summoned vaguely resembles Squall’s description.
As established in my last post, Squall thinks of Griever as a very strong creature, quite possibly the strongest creature of his daydreams/imagination. He says as much in the game. You agree then that it would be highly reasonable that Ultimecia would set Squall up against that thing he considers so strong. It makes perfect sense from a tactical perspective, which is how Ultimecia would be thinking. Why Squall considers Griever so strong isn't up for debate, since he says it himself (see the quote in my last post). As for how Griever looks, well, Ultimecia probably embellished him to make him look even more intimidating.

My argument that TC makes R=U less odd as a theory: Time-travel stories often involve meeting future selves/ fate/ and what seem to be paradoxes. TC makes FFVIII a time-travel story. Therefore it is not that odd to suppose that FFVIII could feature meeting future selves/ fate/ and what seem to be paradoxes.
Not odd, sure, but not suggested to happen either.

I would say however that as symbols within the game, they do still benefit R=U, as the theory offers them an explanation with more substance than simply looking pretty. If you allow for symbolism to occur without the writers’ intent, then they support the theory by indicating it.
There is a symbolic explanation for the wings much simpler than R=U which is really much more plausible. You see, Ultimecia and Rinoa ARE connected in the sense that they both have the same set of powers (remember, this is without the initial assumption that R=U, in which case the game itself says that Ultimecia will inherit Rinoas powers eventually). However, the game shows the two possible outcomes of a sorceress with these powers. Ultimecia represents the outcome where the sorceress turns to evil. Rinoa represents the outcome where the sorceress stays good. This is seminal to Rinoa's developement when she becomes a sorceress; she recognises that she might well go down the same path as Ultimecia. However, in the end her knight Squall is able to save her.

Now where do the wings come in? Well, Rinoa and Ultimecia are symbollically connected through the wings, and since we have already establishes that Ultimecia is the evil sorceress and Rinoa is the good one, Ultimecia gets black wings and Rinoa white wings. It's merely classic good vs evil symbolism where black is bad and white is good.

This interpretation is highly intuitive, implied by the game and far more reasonable (in the sense that it's something Square tend to use in their games). Saying that the wings imply that Rinoa and Ultimecia are in fact the same person is simply taking a far too large leap. The symbolism is there, but it hardly extends as far as to suggest R=U.

PS: If you want a gamescript, you can find two here:

http://www.gamefaqs.com/console/psx/game/197343.html