Hi Jun,
If I understand you correctly, you want to add the GPS data to the EXIF meta-data of each image. This is actually very ideal for anyone trying to use their own post-processing software for those images. When we collected images on a UAV with Piksi, we were using PIX4D to post-process images. PIX4D allows us to import a .csv file which has all the data for each image.
From my understanding, there is no dedicated UAV software that takes a folder of images, and GPS/IMU data and interpolates/adds the precise data to the image's EXIF.
As far as using Piksi multi on the Solo, it is possible but the integration procedure will be a little different. The piksi multi has a very different hardware integration situation compared to the original piksi. There will soon be UAV related Piksi Multi accessories and integration guides. I don't know any exact dates, but most likely in the first half of this year.
Best
Rai Gohalwar