Nanjin,
I would love to see the rest of the TNG crew in FC uniforms like you mentioned, but I would prefer not to see them done the same way Playmates eventually offered them in the 5" scale. They reused TNG heads on the blue uniform bodies and it looked cheap. I'm surprised to see you are considering that as a solution, seeing as how detailed and thorough you have been with the accuracy about everything else involving the figures. You have done tremendous work with just the first figure in the line!
I hope the accurate headsculpts would be offered for the rest of the crew instead, to complete the idea of showing the progression from TNG to the movies; the same way you are wanting to show that with Picard and Data.
Regarding the uniforms: if there is a better way you have discovered since producing Data, I think it would make the line look better. You could sell an upgrade jacket separately for Data, which could be produced alongside the Picard one. If someone wanted to upgrade then they could, if they aren't bothered by it, then they wouldn't have to.
Rather than having stitching creating the lines in the uniform, what about a shirt material like this?
Macy's Alfani shirt
I was in Macy's the other day and came across it. It is a ribbed look like the FC uniform and the lines are very close together, which would work well at a smaller scale. It is also a thinner material that would lay better. It is stitched in such a way that gives a very similar look without the large stitching lines in 1/6
Take a look at the Cielo color specifically on that page, and there is a close up showing the texture of the fabric.
Thank you for all of the effort you are putting in to the Star Trek line. I look forward to receiving Data.