As @alexs as suggested, option 3 looks like the better option to me too as it doesn’t add another scoring system to the already confusing mix. Unless Monzo and/or the community feel it would be in our interest and take the Apple approach of using some courage to develop a new and better system.
Whichever way forward, I think as close to 100% clarity for the sake of the account holder is necessary, something I’m confident Monzo would provide anyway but no so much with regards to other lenders.
I’ve been given this more thought recently. As @anon44204028 has stated that there’d be an uproar from the already existing credit reference providers if all lenders were forced to use a single system as what’s the need for more than one provider?
One possible compromise may be too petition to the government that all lenders must clearly state which provider (if any) that they use as well as clearly outline their lending decision policy, as mentioned by @JamesBell and @anon37165488’s covered in his post in point 7. Even better if they can incorporate our own personal score into their website/app before submitting the application. Having this knowledge available prior to an application would drastically reduce the amount of misjudged applications across the country and therefore would significantly increase overall quality of our scores.
Yeah the stubborn and archaic lenders would boo and hiss that they have to make changes but at least they can stay in business 
Same here! 
In response to Richard’s later post, I’ve edited this to better explain my suggestion to avoid further confusion.