>>"Placing RNA inside a human cell does not sound like a very good idea..."
I agree. The question is what happens to all that residual viral replication matter? Perhaps it's not a problem, but tweaking viral RNA to prevent its reformation into capsid packets for escape seems to be another one of those "unintended outcome" approaches.
introducing DNA?RNA in a cell is offcourse have it's own challenge but imagine there are many many RNA generated (mRNA) daily every moment, what happens to them once their transcription job is over?
They are discarded by cell as waste. So a RNAi particle when it renders a viral RNA/DNA useless that also gets discarded by cells porin functions probably( I am not the expert on this)