The following two letters presumably originate from Square in Japan (possibly an employee). Rusalka and Yuu Miyoshi received the letters and took the time to translate them. Now they've decided to share their information with the site. Thanks, we really appreciate it.
The letters are concerned with Aeris, and sound genuine. Excerpts related to Aeris are shown below.
"...it is not known as whether at some point in the production of the game Aeris was intended to be resurrected, but it seems that this is possible. We found sketches of scenes included this character and others in areas of the game that are only accessable after her death, so this may be possible, though sketches like these are often produced as post-production ideas, before the plot is actually set, and does not affect the future production...'
'...in the original storyline the main character, Cloud, was intended to fall in love with Aeris yet this changed later. This may have caused confusion with the staff and production team therefore resulting in such incidents as the 'Spirit of Aeris' and many others including the Gameshark Cheat, where Aeris DOES have lines. Thank you for taking an interest in Square, contact us...'
The last letter about Cloud originally falling in love with Aeris has been verified in the FFVII FAQ part 2 (by K. Megura), so I believe this is the real deal. Very interesting, don't you think? Even though the letters don't really answer our questions, they at least confirm our suspicions that something was amiss during FFVII's production.