You're not likely to fool a person whose job it is, every day for decades, to determine the cause of death.
You've been formulating your plan for a little while, while the coroner, he or she has been an expert at this for likely their entire career.
I just gotta say it again, these people are total hacks, most of the time (if not all the time). That bullshit about them being experts might play well on TV, but by and large, they're just not.
In the US, they don't even have be actual doctors, and are often elected during election cycles with the other politicians who have no discernable skills or value as human beings. And the ones who do have medical degrees and licenses get paid half (or less) what doctors in a hospital make... so the only people who take those jobs are people who can't get hired at a hospital. Where I live, for example, starting pay for a fresh medical doctor generalist at the biggest health network in town is $200,000 a year (and they're always hiring, because there's a chronic shortage of doctors). Our medical examiners start out at less than $80,000. (It's even worse in other parts of the country I'm familiar with.) They aren't experts, they're the doctors who graduated at the bottom of their class and can't be trusted with patients who are alive.
Most people with a brain and internet access could do a cause of death analysis if they have the right equipment. If you've got a lethal amount of something in your blood, a toxicology screen will find it. If you have ligature marks on your neck, a hole in your head, a sliced open artery or massive blunt force trauma, cause of death is obvious.
If there's no obvious cause of death, they'll shrug, chalk it up to natural causes and move on, which is exactly how FEN (and others) have been using inert gas asphyxiation for decades and leaving a trail of "natural causes" deaths that were actually suicides - nothing obvious in the autopsy, nothing obvious at the scene, and an older individual, so must be natural causes. Incidentally, this is the same reason that elder suicides are so underreported - when someone old and sick dies, most of the time, coroners and medical examiners aren't even bothered to run a tox screen to find a fatal OD.
You're likely to just confuse your family and friends further.
This is true, but it's not because the people examining the body are good at what they do, but because it's really hard for someone to remove evidence after death, so suicides tend to be obvious.