Merge two Videos using FFMPEG and gnu 'make'(or similar make utility)

I have two videos of different resolutions and different frame rates, I want to merge the two together at exact points with as little loss in quality as possible. My idea is to use a Makefile (so as not to have to repeat slow steps unnecessarily) to generate a lossless video of both, re-size to match resolutions, re-sample to insert duplicate frames to match frame rate, cut, paste and even reverse horizontally some of the parts to merge. Then we will compare the timing of the final Video with what we want and adjust the makefile as necessary.