Hi Marshall,
There does not appear to be a way to configure the startup parameter by using the command line. Please see the following screenshot from bpdocs for command line option available in v7.
I would think startup parameters must be set as part of the schedule, i.e. it is considered as part of the schedule configuration than something you would have control of during runtime. It is like you plan to have a schedule run at a time, and all information to support its operation must be supplied beforehand. The moment you start varying startup parameter, you are essentially changing the properties of the schedule itself.
The Automate.exe command line does support startup parameters, but rather when you wish to start an ad-hoc session by supplying with the resource and process you wish to run. It needs to work in this way since you do not get to set those startup parameters beforehand.
In your 2nd question, what is the use case for delaying the schedule? Can you instead starting the schedule at exactly when you need it? As far as I am aware, Blue Prism API available in v7 should allow you to set the start date time of a scheduled session.
After having seen all your questions, I would think you should explore the option of using Automate.exe to your advantage. Schedule(r) may not give you what you want.