tsc (I think it was tsc, sorry if not) already made a plug-in like this. It basically was able to smooth between players POV's and it looked really cool. iirc though it was decided that TF2 is way too fast paced for that kind of transition. Every time the smoothing was used it was really jarring because unlike in CS people move more than a foot a minute, and a lot of things add to smoothing in tf2 being nauseating
edit: just watched the time stamp you linked and the glaring problem is that TF2 doesn't have a 45 second buy timer. People sit in spawn (while 2 classes do static jumps) for ~10 seconds. There just isn't a lot of room to work with there