A common marker could be possible between Prefs only, not the Commons, which had 1.2B shares and no set $$ value like Prefs.
Prefs,....TPS, WAMPQ and WAMKQ had 0($4B), 3M($3B) and 20M($0.5B) shares respectively.
In addition I don't believe the TPS holders would have ever agreed to a single escrow class with the Commons
IMO, the way it was done was the best and simplest way forward.