It doesn't make any sense to use FLM any more. FLM was very memory hungry, and in todays high definition world would be even worse!
A lot has changed about the software we use today. You can now open video files directly in Photoshop and paint on individual frames. You can use After Effects to paint on individual frames, or on long sequences of them.
As you've already found, not much modern software supports FLM. If you explain exactly what you need to do, I'm sure you'll get plenty of valuable workflow suggestions that don't involve FLM.
Agree with Andrew. Nobody uses filmstrips anymore and I can't imagine what you would want to do with it that you couldn't achieve with an ordinary image sequence...
Thanks a lot for your guids, I will do my examinations and let you know.