Well all you say here makes totally sense to me except one thing...
Ever thought about a second Ada Clone? I mean they certainly have the technology to change people to actual doublegangers of Ada. And even if they didn't plan on producing another one, there might be still the possibility that there is a living test subject.
And I can think of a second person Helena and Leon would like to find and protect.
Dabra Harper
the fact that Simmons was standing next to Helena while his "workers" were dragging Debra to the other room made me be suspicious.
So I assume that dabra was made to an Ada clone aswell...
That would explain why ada or rather Dabra ( the one standing behind Leon ) is looking that confused. that would also explain the denotation of "key witness" and the clothing color, cause both are a clone...
And speaking for Derek Simmons it would be a very smart move aswell to let the test subject be killed off instead of his wife, incase the bsaa or Leon would find out about the two Adas.
just a thought...