1. Change of aircraft equipment -> For the love of god, call the pax in advance, or allow the passengers to just change the flight right in the United clubs/1K desk. Don't get them all to the gate to do it. What's the problem of calling the pax in advance and trying to make VDB offers in advance?

2. If scheduling system assigns the crew to be at specific flights, they better book them into the flight, and the crew better be on time. If they try to get on the flight in early stand-by, under no circumstances their seats are called 'booked', and in no way they can pull a guy off the aircraft. If they are late to the original scheduled flight, tough luck, either arrange the transportation by themselves or ask UA if they can work something out with the crew who is late.

3. VDB - Can be at the gate or onboard. IDB - Better be only right at the gate. Worst-case: You would have to IDB the pax onboard only if the stand-by pax who got cleared but the original pax who reserved for the flights are ontime at T-15, or T-15/20/25 INTL, depending on the airport. If crew is scheduled to be on the flight, they are treated as the booked pax, and shouldn't be on stand-by(This also confuses me why the heck those crew members need to get on the flight but they are not booked to begin with.
No way in hell the crew members are on standby if the crew scheduling system tells them to get on that flight.) Just cut it if you are minutes late, take the next flight.

4. Increase the bump. Take a look at what DL is doing now. If DL can make $9950 possible, please don't tell me UA can't do the same.

5. Politely, and please may I add, politely, explain to the IDBed customers what's going on. If you limit the IDB to be only at the gate, you actually save a lot of hassle to have to forcefully remove the passengers onboard.