I have read all the story, and don’t understand how your multiclip edit was so Hard. FCP handles it EASY as it possible just as:1-2-3. Even when the footage is synchronized in timeline – Razot tool, select all – make multiclip and BAM. Even if not created shortcuts – you can assign them to your desired function keys + 1(for track1) 2 for track 2 and so on. and then press play and work in linear mode. cut everything in realtime.
Another solution is yes – the best in sync. – Plural. but when making it in HD, 12cams, and 3hours concert… this is fu*** crazy.. you can go home to eat or cam take a cig to “smoke” 🙂 its hard if working with Canon non converted footage. but.. everything can be done.