I couldn't read the rest of the post, but the first line is incorrect. You don't need Automatic transmission for this.
Adaptive cruise control only comes in 'very few' cars (like Audi A4 etc) and a few high-end cars from Toyota. Adaptive actually changes the speed for you when its needed.
However, for simple cruise control (which just fixes the speed at a particular point) you do not need Automatic Transmission.
1993 Accord came with manual transmission as well as cruise control. Honda Civic manual came with Cruise Control (not in Pakistan). Subaru was the first car company to provide manual transmission cars with cruise control in Australia.
It simply disengages or turns of Cruise Control as soon as you hit race, brake or clutch.
So yes, automatic transmission is not required for cruise control.