Receive Location and Orchestration – 2 scenarios

Hi folks, my setup is as follows. BizTalk receive location published
as web service. The receive location accepts messages and publishes
them to the messagebox. An orchestration subscribes to these messages
and processes them.

I need some advice on implementing the two scenarios below:

1. How do I configure the system so that I have the flexibility to
receive messages throughout the day but the orchestration is only
turned on for a few hours a day? e.g 2pm to 4pm, messages are sent by
external systems to the receive location. 4pm, the orchestration is
started and it starts to process the backlog of messages
automatically. I cant disable the receive location because the
external systems will then get errors when they submit. Basically, the
submission should work but the processing should happen much later.

2. In such a scenario, where there are a significant number of
messages awaiting processing, how do I specify that messages of a
certain type should be processed first (a priority system)

Crossposted from Google Groups for more visibility, thanks!