In David Gerrold's novelization of "Farpoint," Data was built by aliens...
Yes, that was the original plan from the TNG bible. Data was basically a recycling of the android Questor from Roddenberry's failed pilot
The Questor Tapes, and Questor was descended from a long line of androids seeded on Earth by aliens to guide our development.
Also in the original bible, Riker was called Bill and was prejudiced against Data (which was a significant thread in
Ghost Ship), Data's name rhymed with "that-a," Geordi was a liaison with the ship's children, and Worf didn't exist. Data was also intended to have an Asian or Pacific-Islander appearance, but they didn't stick with it. Memory Alpha says they did consider a few Asian actors -- Kelvin Han Yee, John Lone, and even actress Kim Miyori -- but also a number of white actors (including Robert Englund, Mark Lindsay Chapman, and Eric Menyuk) and even Kevin Peter Hall (who was Leyor in "The Price" and the title character in
Predator).
By the way, I found an early casting memo for TNG:
http://www.lettersofnote.com/2010/08/star-trekcasting.html
Some interesting alternatives there. They considered Yaphet Kotto for Picard. Julia Nickson and Rosalind Chao were considered for Tasha. Candidates for Geordi included Tim Russ and, of all people, Wesley Snipes. (Odd that they were determined to cast a black male as Geordi but were more flexible with the other characters' ethnicities.) And Jenny Agutter of
Logan's Run was considered for Dr. Crusher. It also lists Denise Crosby as the only possibility they'd found for the role... of Troi.