You are not limited to 3 cuts, we only look if the value is the same on the two frames we request.
You can animate A,B,C,A,B,C,…
If you have a movie edited at FPS with cuts in it, no need to split apart
Drop it in sequence 1 15 PFS, double speed with Premiere as I suggested
Drop that sequence in a new 30 FPS sequence (say NO when Premiere asked you if you want to conform), in Twixtor Source Display mode, mark cuts
Then type 50% in Twixtor Speed
Does that do what you want? 10 seconds will remain 10 seconds like this (and you will have 2 times more frames)
Pierre