Leandro, would you feel okay sharing your script, too? I'd love to see how you manipulate the CoH client via a script to run the demos.
There's really nothing to it. I go through a list of all the MOVs (that Codewalker dumped in the Wiki) and write a demo file with that MOV, then I just call
D:\\CohBeta\\cityofheroes.exe -demoplay mov_list -demofps 30 -demodumptga -fullscreen 0 -screen 720 720
to dump the demo's contents to a folder of TGA files, and then
ffmpeg -f image2 -r 30 -i "D:\\CohBeta\\client_demos\\screens\\mov_list\\movie_%05d.tga" -vcodec mpeg4 -b:v 800k -r 30 "D:\\All the Dog MOVs!\\$mov.mp4"
using the standard ffmpeg static .exe to turn some TGAs into an MP4. There's absolutely no special scripting here, just go through the list, write demo, dump, convert, repeat.