That is a very interesting idea. And it works as transparent icon means there is nothing visible on status bar per say. But the downside is that, when the user pulls down the notification shade, he will see a notification with title, message and everything except the icon, which looks a bit awkward. Nevertheless it works.
But I still believe there is a better way to do this. I am attaching 2 screenshots from the open source ad blocker called
Blokada. It's minSDK is 21 and targetSDK is 27 and so it is compiled for Oreo. Both screenshots have been taken while Blokada is running.
In the first image, if you look at the statusbar at the top, you can see that there is no notification icon related to Blokada; only the usual icons such as WiFi, Bluetooth etc... Now this can be achieved by using a transparent icon for notification. But if you check the second image, you can see the Blokada notification running. And what is interesting is that in the first line of notification that says "Blokada . now", you can see its icon to the left. If you use a transparent icon, that icon on the left will be a blank space. But somehow Blokada is able to do both.
And this is what I am trying to achieve.