They had a general plan, but it wasn't that! But, the plan was that Delgado's Master was going to die, and there was going to be the hint that he died to save the Doctor.For awhile (decades ago, mind you), I honestly thought (due to some dubious "facts" I read somewhere) that was one of the notions considered during the Pertwee era, before Delgado's untimely passing.
At any rate, I don't think tinkering with their relationship in the joking idea I mentioned would be a good idea. Let them be childhood friends who took different paths and don't mess with that!
I don't know what the big reveal will be about "it's all lies" is, but I'm thinking it has more to do with the origins of Time Lord society and their time travel abilities. Maybe not quite the story Time Lord kids are told! Maybe they stole it from another universe? Or, maybe humans evolved in the distance future to become Time Lords, subconsciously explaining the Doctor's fascination (and the Master's to some extent) with Earth and the physical similarities.