I have a very similar goal and a service like Relay.tools has almost everything already to make groups on relays happen. And it works. 

NIP-29, however, overcomplicates everything by not having a 1:1 relaytionship with the group and copy pasting big-tech UX (Telegram etc...) that doesn't make sense on Nostr. None of the current apps work or have a clear goal. So why would relay services bother? 

More on this here: nostr:naddr1qvzqqqr4gupzp22rfmsktmgpk2rtan7zwu00zuzax5maq5dnsu5g3xxvqr2u3pd7qyt8wumn8ghj7mnfv4kzumn0wd68yvfwvdhk6tcpz9mhxue69uhkummnw3ezuamfdejj7qq0wd5k6urvv4ch2etnw35k7mnnuquu5l

I might be Naive Nieling this, but I wasted a lot of time believing too much about the NIP-29 hype without checking its assumptions.