[pawel]

as along as the SA is capturing to mpeg2, any video editing done (be it necessary or not) afterwards re-encodes it.

Of course not. There are many (free) tools which allow to cut on the GOP level without any re-encoding or on the frame level which re-encode just a few frames of the GOP being changed. For example VideoReDo is so good as you won't notice any re-encoding, no matter what (high) quality/bitrate is the source. Audio can be replaced separately, so no need to touch the video part.