Hello Yvonne,
please find below my answers:
1: The service location 'On site' is currently hard-coded, however in future it is planned to be more flexible. Unfortunatelly an add-on will also not help here, because the current rule is that the service provision location cannot be changed once there are items, which is the case right from the start when a direct follow-up from contract is done. The only way to overcome this situation is to first start with the service order and then link the items from there to the contract items.
2. This is a well-known limitation and as you said, currently two service confirmations have to be created.
3. Unfortunately the use case you described is currently not supported. What I wonder is if you can still use the on-site option together with pick, but set the ship-to party (Involved parties tab in service order) to your own company and site address.
In additon I recommend to raise an idea in the ideas place. This is constantly monitored by the development colleagues.
Best regards,
Stefan