agree.
to the general “broadcast approach” - i’d like to get one step back and have a look at the broader picuture:
- “broadcast” as suggested here are used in whatsapp and in threema (“distribution list” there) - somewhere else?
- telegram has “channels” instead, whatsapp has “restricted groups” which are similar to telegram’s channels (but have no invite-link, are still private)
- signal has nothing
- with some discipline of the group members, a normal group could do the job as well, just creating a group “homework” might do the job in the initially described scenario. maybe not perfectly, but still.
- there is forward-to-multiple-recipients. for a birthday-invitation, that would be fine, but for everyday use, this is not a good solution, sure.
if we put away the fact that channels in telegram can also be used for huge groups, have invite-links etc., channels are similar in some aspects:
- they also try to hide the complete recipient list
- recipients cannot answer to the channel
otoh, of course there are differences:
- channels do no hide the fact, that they are channels. recipients of “broadcast” are not aware that they are in some list.
- the reply chain is clearer as you just cannot reply in a “channel” - for “broadcasts” replies go to the one to one chat which might be confusing.
- channels might raise more expectations (invite-links, huge channels etc.), this is probably not true for “broadcasts” that we can implement more or less exactly the same as known by whatsapp.
implementation wise, there are probably no huge differences, there will be lots of tiny changes needed in both approaches, it will be some work.
i just came over all that that because the mentioned “read only groups” suggested at
are closer to “channels” as to “broadcasts” 
finally, i am not saying that the one or the other is better, currently i do not have a clear preference, ±0