Since i don't make combo videos, i don't bother with having a specific amount of meter, i just count the stuff i put in there. In a combo video however i think you should start with the number of bars needed to start the combo (not the number used, if they differ) to show how much meter is needed to start so people can see when it becomes relevant and how good it really is.
In my opinion the opponent should start from zero meter because from a gameplay perspective the opponents meter gain is important.
If you want to try and make an HD combo that goes back to building meter, try Takuma and end the HD section by bringing the opponent back to the ground with zanretsuken into command throw, that way you get a good number of hits after HD has ended, might be enough to build an extra bar.