Well, for most part I figure it's fine, though... I feel like you missed a pretty essential part of my input on your initial idea. Right after a bunch of mulling over Bloodborne lore and theory, I wrote:

[QUOTE=Dark Jack]Short version: it might be possible if the character was a Yharnamite before, [B]not a Hunter[/B].[/QUOTE]

The whole point of that entire theorizing-part and the conclusion after was that it's highly unlikely that it's possible to turn a Hunter into a false Paleblood Hunter due to their resistance to disease. From the biography you wrote I can tell that your character is still supposed to have been a Hunter before volunteering for the experiment.
We [I]can[/I] go with that, if you like, but you'd be entering even more unknown territory than just regular false Paleblood Hunters. [I]And[/I] your character wouldn't be in the clinic with all the others, since he wouldn't be rendered comatose by the metamorphosis, since he isn't actually changing. Someone would just give him an injection and tell him "go die and see if you survive".