Above bench basin complications

Hi all
We’re on the selections journey at moment and looking for some insight on a complication we came across today.
In our ensuite we’re really hoping to have above counter dual basins. The style we have been aiming for is a thin edge rectangular basin. It turns out most of these don’t have overflow holes (we found one that’s 600mm long - but two of those on our 2000mm vanity seems too much).
We were told we can’t have the basin without an overflow. When we pressed, we were told it means needing floor waste as huge expense and possibly additional water proofing.
To add to this, we were also told that because were going 600x600mm tiles on our floor, we have to have channel waste, again at great expense. We were told the tilers can’t get adequate fall, using a 600x600 tile for a standard waste unit.
Totally out of our depth here. Any thoughts/advice would be greatly appreciated.
In an ideal world, we get to have our above counter basins!
Thank you!