One thing that Bristol had, that Armstrong-Siddeley two-rows never had was licensed production. Italian and Japanese companies produced some Lynx and Cheetah clones, but nary a Jaguar or a Tiger. It has already been mentioned that Alfa-Romeo double-rowed the Pegasus with a failed engine. By a more serpentine and circuitous route, Gnome-Rhone also two-rowed a Bristol engine, resulting in the engine that Alvis wanted to clone. The Bristol Titan was a five cyl engine that was license-built in France, and ended up out-selling the British units. G-R tired of paying fees, and modified and modified, resulting in the 14K. They stopped paying fees in 1930. So there's another two-row Bristol, coming home.
Another engine manufacturer that is a miss is Wolseley, a car company that built the V-8 Hispano in WWI. In 1933, they decided to get into the biz with Zodiac engines, beginning with the Aries, and planning bigger, but not two-row engines. They wrapped up the show a few years later, unable to compete with the little A-S Cheetah and Lynx. Could a two-row Wolseley Pisces have been a contender?
I have mentioned that development on Perseus had halted for lack of application, but will add that Taurus development was also curtailed, mostly due to reputation. In fact, tooling had gone to aid Napier Sabre development. In fact, it was found, and patented, that a centerless grinder with a worn out grinder was perfect for making sleeves. Serendipity. I found this out, because an American sub-contracter's start of production was delayed when they had to send their tools to England. Also, the major problem with Taurus failure was the Maneton Clamp on the crankshaft, which was subsequently double-bolted, and patented, by Roy Fedden, providing the fix, but without finding new users.