This really sounds great! Count me in!
So your hope is if there is enough response RCG we may get a dedicated category for 1.5M and smaller.
May be good to start talking about the launch because that determines needed space. You are lucky to have so many large parks.
The term Zip-Start gets used for Hi-Start but they are different. One supplier of The Zip is Aerofoam. It is 15' rubber, and 25' line and can be used in 100' space.
I don't have any experience with these, but they sound to me like a lot of pull, lot of speed for jets, etc, and some risk. As you know the smaller HL ships can are hard too hold with a lot of pull. In a public park you also don't need the pin becoming a missile.
Sky Bench makes a good mini hi-start, but I don't recommend it any longer because of price and his high shipping cost.
Probably best may be the Dynaflight Up-Start which is 25' 1/8" ID rubber, 100' line with chute for $28 at Tower.
This one needs min 300' launch space.
I'm searching for a source for mandrel formed 3/16" thick wall UV protected tubing.
There's not much to building them. Maybe somebody's wife might start a cottage industry for the chutes. I have a small one that works good. Not a wife, but a chute.
I guess that's enough for now.