Very fascinating analysis Nite.
I though at first it might be Ashley because if you listen to her voice it sounds exactly the same and Ashley was a teenager at the time,
I then realised that there was no connection of how Ashley could be there.
I would love it to be sherry and we will get to learn more stuff form the past
It could possible be Alex because he sounds a little more sinister than Steve, plus it looks a little different from Steve.
The blood thing may be bang on money because the guy does say something like if they want me they have to come and get me and then
says something about selling his blood to the highest bidder.
Some nice theories you got there

If the game is supposed to be 10 years after the raccoon city incident (only a speculation) then that would make Steve 25
so I'm pretty sure he would be way passed puberty by then.
I would like to see Steve in a game again but I would not like to see a dead character return to life.
Although we dont know for sure he is actually dead, I mean he dies in CV but Wesker also tells Chris that there is a chance to revive him,
thus meaning he is isn't fully dead because the virus inside him will probably still be very much alive.
Wesker also sold Steve's to Javier Hidalgo which he used to infect his daughter Manuela (if you have played DC you'll know what I mean)

So it could go either way as Nite pointed out because there is already evidence of Steve's blood being of high value and has been used to make profit.
Although it also could be Alex because if he is infected the same as Wesker then you can all realise how important his blood and personal being would be.
Sherry was also captured by Wesker so that would give more of a favour on Alex's side because when he escaped he could have took sherry with her.
She is also a character of high importance, since she being the daughter of the G virus's creator Mr William Birken himself

haha
Would be shocking but at the same time hilarious if she turned around mid game and it was him, all rough faced and stubble with a blonde wig on

That is a valid point.
I think they will most likely set "it" as a male character though.
Although would be cool to have a female character that kicks ass much as wesker or even better