Using PVC tubes
Is it possible?
Yes! But will take a bit of work to connect the ball connectors, some people have done it successfully.
Attaching the ball connectors
1. Captive nut and glued-on end caps
You'd need to replace the wood screw with a machine screw to work with the captive nut.
The wood screws are 4.5mm x 65mm for reference.
2. Fill the ends with resin
Once this is set you can screw the ball connectors on with the wood screws.
One buyer used clingfilm and gravity to get the resin to set flush with the end of the tubes.
3. Insert a section of wooden dowel in the ends
You could glue it in or insert a screw or pin in the side.
Doing both might be safest.
Soft-wood would be simplest as you can just screw in without pre-drilling.
One buyer found Gorilla Glue worked well.
What size of PVC?
1 inch Schedule 40 is a good bet.
You could go to 3/4 inch or 1/2 inch, though they would suit smaller diameters where the sticks would look chunky at 1 inch. The smaller diameter tubes wouldn't be as strong.
The inner diameter of the 1/2 inch tubes would be about the same as the base of the ball connectors (16mm), with the outer diameter around 21mm. So this is probably about as small as you'd want to go.
Here's a link to a table with measurements for Schedule 40.
Are we making ball connectors for PVC tubes?
Not at this point as it will take a significant investment though it is something we like the idea of.
End caps approach - thanks to Alec in the US for sharing his pics.
It keeps the weight light which reduces stress during the build.
Not sure how she attached the ball connectors but the tubes look like they are a similar diameter (even a bit smaller perhaps) than the base of the ball connectors.
Also a neat approach to fix the position of the base ring; larger cylinder through which the struts pass fixing their position in relation to each other. She also added an extra later for a bit more height in the same footprint. Similar to the pod approach.
Thanks to Akio in Japan for sharing her pic and clever approach!
Thanks to Edwin in Germany for sharing his dome and tips, he glued some inserts into the ends of the tubes. He'd suggest a cross-pin to further secure the ends in case the glue fails. You can see an example of this approach on the Working with bamboo page. He also managed to bend his base sticks to make them circular, very cool!