Well, if it was my laptop and using it for video editing and music production...and I had room for two hard drives...
I would replace the SSDs with the largest hybrid hard drives I could find. Right now, the largest ones commonly available seem to be 750GB.
Or another idea would be to get a 750GB hybrid hard drive, use that to boot off of. Then add a 2 or 3 TB regular hard drive for file storage.
For video editing, I believe your main bottleneck will be your CPU. So I don't think downgrading to slightly lower performance disks with more capacity will be a problem...