We won't be contrinuting under the WA, so one of your points is out there.
AS for "parked in the backstop till they see fit to let us out" well the backstop is there only if a deal is not negotiated in time, and has to have both parties agreeing to its end, not just the UK.
We want to continue under the WA in the Customs union, which means that we need to follow ECJ rulings. We can choose not to once we the period of the WA is agreed, but most likely we are going to still follow them. Without the WA we are out of the customs union and the lorries are queuing at Dover.
Funnily enough, in the trade deal with the EU the UK is going to be a rule taker, as it will be with the US, and any other trade bloc. Also any trade deal will have a court of arbitration that will cover much the same.
"No WA for me; I think we should leave and then negotiate an FTA"
I'm not sure you understand the implications.
Or just don't care cause it doesn't effect you.