I haven't let this drop, I guess I'm just too dumb to let some things go.
So, been doing a lot of thinking on this and I've decided that I am going to move the battery to the trunk and use a Ford style starter solenoid (also in the trunk) to engage the starter. This doesn't completely remove power from under the hood, but even if they jumper to the ignition system off the alternator stud, it shouldn't allow for anyone to engage the starter. I guess someone could bring their own battery, but I don't expect that many car thieves walk around with a battery under their arm, and if they knew to bring one then they will probably bring a roll-back instead and steal the car regardless of what else I do.
In addition, I am wiring in a switch inline with the starter circuit. I've left off most of the details of how (this is the internet), but will say it is a magnetic switch rather than a push button style. So, as long as the magnet is in the right place, the circuit will close and the car will start, and when I want to disable the car I can grab the magnet and put it in my pocket. Need to figure out how to shield that, though, so I don't demagnetize the cards and such in my wallet.
What I wish I could find is an RFID relay of some sort that just closes the circuit when a fob is in the car, but the only ones I've found are kind of expensive. Shouldn't be hard to swap in the future, though.
And yes, I am leaving the amp gauge in place for now. I know it could be an issue later, and if I do more upgrades I will probably bypass it, but for now I am running a stock system with no additional loads so I am going to leave it alone. Not putting a volt gauge in the dash is one less project right now and I don't see that it is a real issue at this point in time.
So, here is a clip of my proposed wiring changes. Any input? See anything I missed? Wire sizes seem ok?
Last thought would be to add a buzzer or trigger the horn or something by using a SPDT relay and use the NC post to send power to a noise maker and the NO post to the solenoid when the circuit is closed.