Yes, the proportional size is the most important to me too. The others are more of an inconvenience.
Combining them correctly will get you two stacks that are equal.
Plus, they all fit into the 32mm system. You build storage cabinets based in that and they fit.
My first experience with this was the RO125 which came in the new sized Sys3 that is bigger than the T-loc 2 that it would have been in before. This screwed up my system. I made it fit by dropping the drawer slides down to the bottom of the cabinet, but that's not in the 32mm holes.
The front handles are of no use to me, or anyone with Sys-Az drawers.
The top handles "snap" to keep them from rattling in the truck with the Bott racks.
The handles swing foreword to keep them from snagging when sliding in the racks, again no need it the original system. When the drawer is pulled out to access a Systainer, the handle naturally falls to the back, so it doesn't get in the way when pushing it back in either.
The Bott racks are for truck storage only, they are not intended to be opened/accessed, like the Sys-Az, or shop made drawers. Again, not the original intent of the system.
Tanos could make a line of Bott-specific models and leave the system the way it was.