Bert, A Grin Cycle Analyst control/display (
https://ebikes.ca/shop/electric-bicy...-analysts.html ) could very likely be added to your existing setup to provide either a power based PAS configuration (which feels MUCH more natural than most other PAS setups) or using one of a wide variety of torque sensors (most are replacements for your bottom bracket). The CA would be placed (electrically) in between your existing controller and the PAS/torque sensor. The CA also handles the throttle input. It basically takes input from a variety of devices, determines what you want to do and outputs a throttle like signal to your existing controller.
Not entirely simple but it would allow you to keep your existing trike setup.