if you break it down into injection moulded parts - then yeah, plenty modifications.
But then you'd have to expect people with 3d printers to buy them. And most would simply just print something else - there are no shortage of clever spools around. Or take one look think 'that's a good idea' and design their own - like i tend to do :-)
I think that's the only one print expanding one. But I don't know for sure.

Like i think my bottle bird feeder is the only one with hassle free bottom loading, but don't actually know. Or my 0.3gm trolley tokens are the lightest in the world and cheapest to print, but it's just a guess.

It's an interesting conundrum. Do you put your designs up on a pay per download site and hope nobody else would rather design from scratch than pay a few sheckles. Or sit umming and aahhhing and just not making any decisions at all - like me.

So I guess the other approach would be along your lines. Design something, test with 3d printing and then try and get someone in the injection moulding industry to buy it from you.
Have to think about that one.