MUSIC/SOUND:
since a replay you create doesn't have any sound how about importing music or sound while rendering or something? Maybe after rendering a little message would pop-up asking if you would like to add sound, and if you click yes a simple video editor would appear for you to add sound to?
I use replay to create 360 videos and it's really hard to find a video editor that won't add the black bars of doom or make the quality look like a fuzzy mess. plus you won't have to wait 5 million years to render the video then edit the video then render the edit then upload to youtube or somewhere... Something like this would be useful!
FILE TYPE:
ok, MP4 is great and widely used and supported but they are generally quite large and it's hard not to lose quality when compressing... maybe add an option to change the filetype? like a .wmv or .avi?