Plausible to me.
However, you are certain of that because . . .
Because I know that somewhere in a government lab they are not 20 years ahead in knowledge and technology. More like the scientific equivalent of the DMV.
Moreover the genetics of HIV is just like SIV, other than adaptive mutations that make it more able to infect a human host.
No scientist would know, even now, what changes would be adaptive and which would be maladaptive.
Thus the only way to change it wouldn’t be through “bioengineering”, but through infecting people with SIV and allowing it to adapt to become HIV.
It is sort of like trying to make the perfect baseball player without ever having him play baseball - the easiest way to “train” him would be to make him go out and PLAY - not do exercises some egghead thinks will make him a better player.