You missed what I said. The first event isn't to end until 4:30 which is the same time the reception is to start. So how can it start on time. We won't be able to load in until the people from the first event are out of the room.
I said my first issue was with how the venue is treating this couple and their guests. It's wrong and they need to be punished which probably nothing will happen. Something would happen if it was my wedding. If I had to I would go to the news media and tell them what happened.
And YOU missed what several other have TRIED to explain.
There is an hour of cocktails in another room.
You will need to (try to) load in while the other event is cleaning up...
so there will probably be another DJ loading out...
and the wait staff will be clearing tables and putting out new place settings.
It will make things different, it will be confusing, people will be getting in other people's way...
but you can make it work.
As for the venue pissing off the clients, don't sweat it. You have your issues, they will have theirs.
If anything, the screw up with the venue will distract them from any problems you may be having.
I had a venue that tried to do two events in one day. THEY only had one room,
so me, my gear, and all of the guests were standing in the parking lot until they were ready.
(they were offering free drinks to the guests, while they waited in 90-degree heat)
And it happened more than once.
I, too, have venues nearby that pull some pretty crazy sh*t.
But they are still in business, and not hurting for bookings.