One of the frustrating things at the moment with the X-T1 is the Multiple Exposure feature.
Great that it has it, but you can only use 2 images, it outputs as JPEG, and there is little control of the blending.
It would be a great Kaizen feature for Firmware 5 to have:
1) up to 5 or 7 images (some manufacturers do 9)
2) Output as Raw
3) Blend control
No idea how you submit features for consideration, but I have tried a few tweets.
What is slightly frustrating is that the X-E1 had Raw output, but the flagship model doesn't. I guess too that this isn't restricted to the X-T1 as X-E2 owners would benefit.