>>718274962
The original plan for 4 was always for Spencer to be the main antagonist and then die.
In Kamiya's version, Dante and Vergil were originally the twin sons of Spencer (obviously not named Dante and Vergil), and it would be about one son, Tony Redgrave (Dante) killing his dad, who is a semi-immortal beast of a man.
You can see this original idea for Spencer in the concept art of DMC, but even in the Trevor Files that got published with the Saturn version, Trevor calls Spencer an 'imposing man' in regards to his physical presence- which is certainly not the case come RE5, a mere 8 years later on the timeline.
The later Leon versions had Leon, in 1999, investigating areas around Spencer's castle, and there would be an HCF raid on it which would lead to the events of the main game where Leon is infected and Wesker's HCF squad is, once again, wiped out.
I imagine that, outside of Ada, a lot of release RE4 isn't too dissimilar from what was planned. Just switch Saddler/Salazar out for Spencer, and maybe Krauser for Wesker (we just don't know that much about non-Leon and Spencer roles). The obvious plan from there, based on 4 itself and RE5, was for Spencer to die and Wesker to continue his rise in the Rival Company, now that he's toppled Umbrella in addition to securing a t-Veronica sample.
And yes- Umbrella would be gone. That was always the plan.
>>718275071
Would take too long to go over.
CV has a lot going on that people don't really get or appreciate, and it's the best connective tissue from the reserved style of RE1 into the ideas brought up in RE2- the ideas of superhumans made through viruses, which become Alexia and Wesker (and of course, Spencer was always that).
Zero is weirder and harder to grasp, but an idea to chew on is this.
Ultimately, it is the story of a man forgotten and then subsumed by his creation (Marcus). Billy himself is also forgotten by the end of the game, and Birkin suffers a similar fate to Marcus.
What of Rebecca and Wesker?