Unionize — interesting idea. There are similar ventures out there, such as brew.com. A union and Brew both need a critical mass of podcasters selling content to be viable. Both use payments to benefit the whole. But Brew has the tech part built — a union would definitely need tech for supporting all the features you mention.
Regarding tokenized feeds that Patreon has — I think they are pretty successful so far. People don’t want to abuse them because they want to support their show. Chapo Trap House makes upwards of $120k/month with their private feed on Patreon. I think there does need to be a better protocol in place which incentivizes podcatchers, while also directing listeners to tip or pay podcasters in-app. I’ve thought a lot about this in the past and I came with something I call Pod-pay.
But it faces a barrier that Brew.com and all the other premium podcast solutions face — App Store and Google Play terms. To sell content subscriptions in a podcast app, Apple and Google take a huge cut — 30%/mo. — which, after you take out any other service fees, leaves little left for the creator. If Apple and Google were to change their terms around content subscriptions, it would open big doors for creators.