I use common bus with no problem, with frequent out rail drops and the ground for accessories. I have much larger "loops" than you do, and use one TIU channel for each It's not hard to break up into 3-4 blocks per loop, and gives considerable opertaing benefits. Just run a length of 14-gauge (what I'd recommend on a layout of your size) to each blocks and sever the center rail between blocks.
Can motors are not current hogs. I don't know why you say they need high starting voltage, You should have had the old Lionel Pulmor motors.
