As for mocking suicide… I think you’d have to talk to a professional about what they do it. Given David Kelly, Epstein, and many other high profile cases, it does seem to be as difficult as you imagine.
The inquest concluded his death was "unnatural and likely to have been criminally mediated" though with to little evidence to outright state it was an unlawful killing. The police eventually decided he'd likely locked himself in, despite the lack of fingerprints on both the bath and the padlock having made it a rather extraordinary feat for him to get into the bag and lock the padlock.
Which to me goes to show that whether or not you get away with faking a suicide likely has relatively little to do with how well - or plausible - you fake the suicide vs. how well you sufficiently prevent a link to yourself and the power you have to prevent a proper investigation.
At least in the case of David Kelly the circumstances were plausible.