It won't be the last one. Next would probably be a system that is the most hexagonal possible. BOX was originally susposed to be only loops that enter the square of the grid, and only Tubes could pass between the Squares outlines, it turned out to be the most compact ultimion maker i ever made
a 15 square Mechanism.
(it wasnt susposed to be compact which is ironic).
BOX wouldn't have been possible without the Ability to overlap the elements constituing the Accelerator. It make the building neater and looking safer.
A good idea to what to add may be to add somesort of mix between the curved pipes and straight in the sizes of the Curves, basically the Straight will only be input while the curve will only curve towards the exit of the straight
Sorta like a backward Loop exit diverger but with differents sizes. maybe along the way the other sides for the divergers as well aka mergers