2 - 3 diameters is tight; plastic or metal. You’re going to get a lot (relative) of flattening on the inside radius of the bends, not way around that. The problem with plastic is that it just doesn’t like to bend, especially without heat. And with heat, it just tends to flatten out completely.
To reduce the flattening of the inside portion of the bend a ‘mandrel’ bender is the tool you need. I’ve never seen one that is for 1.0" tubing; that isn’t saying they aren’t out there.
If you are not familiar with a mandrel bender, it has a form (the mandrel)that looks somewhat like a string-of-balls that goes inside the tube before it is bent. After the tube is bent the mandrel is extracted. But again, the ID (inside radius) is generally greater than the 2-3 diameters that you need. The problem; as the bend radii get smaller, the tube tends to start forming itself to the internal mandrel and (eventually) locks it into place (not a good thing; and almost impossible to extract with out destroying something).
I managed to fabricate a couple of small radii for a motorcycle frame by filling the tube section(s) with sand and then welding an end-cap on each end; the end cap on one end had a small (.062") hole to allow for pressure relief. The tube was then heated cherry-red all around, and bent. The end caps were then cut off, and the sand dumped out (the tube was cut over-length to allow for the end caps, and removal).
The flattening was minimal, but as you can see the method is far from ‘production.’
You could use solid bar stock and get just about any bend radii you wanted, but obviously weight would skyrocket, and with it expense (of fabrication, and ultimately, shipping).
Will your product allow you to devise a ‘connector’ with the appropriate radii and then use straight sections of tube? It sounds expensive but straight tube, cut to length, is cheap. The total production volume, and number of different bend radii/angle combinations (each connector requiring a separate mold) would be the determining factors as to feasiblilty.
Just a thought: make a mandrel of the inside of plastic tubing, using cast, flexible urethane material. Then gradually heat the tube and bend it. Without exterior support (which the bending ‘die’ provides to metal tube) I would expect the exterior of the tube to distort, but it might work.