So my 2003 Outback got wrecked and I'm looking to buy another Subaru soon and still have plans to do a high compression N/A build which will require tuning.

I might buy a newer 05-07 legacy or or 06-07 Impreza so I can just tune the stock ECU and avoid any headaches with OBDII inspections here in NY.
But I really like the body style of the 00-04 Legacy and might go with that even though the stock ECU is not tunable.

So I know the typical workaround for OBDII inspections with standalone ECUs is to swap in the stock ECU every 2 years, get the car inspected then swap back. Kind of a hassle I'd rather not deal with. But would it be possible to have both the stock ECU and a standalone installed and wired in the car at the same time with a switch to change between the two? Flip the switch and it cuts all power, inputs and outputs from the standalone ECU and switches to the other. Once the inspection is done and passed, you flip the switch back. So you get the benefit of changing ECUs with a simple flip of the switch.

Also, if you run high compression pistons and other mods that require tuning to not kaboom your engine, wouldn't you have to swap all those parts back to stock when changing to the stock ECU for inspection? Wouldn't you blow your engine on the way to the inspection station because of the higher compression and stock tune?

Sorry for the noob questions, I'm still very much trying to find my ass from my elbow when it comes to tuning and electronics on cars.