I thought about this feature also, but I don’t think this is valuable right now. This feature will put on another one, to cut several seconds at the end which isn’t possible to predict and require to run edit on already recorded file. Which brings us to implementation of some sort of video editor and this one adds over complexity for a simple app.
I like the idea, but I’m not sure that I’m able to implement it soon.
Right now I’m more interested to add basic features, like rotation (to be able to record landscape mode). It is portrait mode only at the moment.