Dharke sathi,
I see very very low possibility that the accused officers will drag the ministers and secretaries at the Home Ministry. If you have followed up another news in Kantipur today, it has quoted one of the accused officers that ' he will reveal the involvement of ministers in the court if they will be only ones to be convicted in court's final decision'. But, i dont think he will do that. In case he does that, court requires the proof that the specific minster put some pressure on him. Obviously, there wont be any proof whatsoever. So, a person who knows all these court procedure wont blame minister/secretary.

The only way those former minsters could be indicted is through another case accusing them of having property that is disproportionate to their source. The case similar of Chirajibi Wagle.
The way you suggested: To track down the Money Notes that could have been given to ministers or their assistants by this Bharati guy, this could be possible theoretically, but i dont see any possibility of doing that.