As the title says, I'd like to move the:

Ignition key module (what is this properly called?)
Tank will be moved wholesale
Lock will be pulled from one bike and put on the other
Helmet lock will be pulled from one bike and put on the other

So, really, the only thing I have a question about is that first part: How do I move the ignition key module off one bike and install it on the other?

ignition (it is the main switch and steering lock) is held on by 2 bolts and has a single plug pretty straight forward plug and play.

AWESOME. That's great news.

On the other hand, that makes this bike ridiculously easy to hotwire, doesn't it? How does the steering lock work if it's that easy? Maybe I'll figure it out here in a minute when I do it.

steering lock is a pin that pop out of the lock cylinder and fit into a hole in the steering neck when you turn the key back to the lock position and have the bars cranked to the side. As to hot wiring, most vehicles especially older ones (a lot of newer ones have sensors in the keys that make it difficult) are ridiculously easy to hot wire if you know how.

Yeeep, it's just that easy

Interesting. Just a pin, eh? So when thieves steal a bike and crack the steering lock, they have to snap that pin.

Someone older than me was telling me I could "hotwire" my bike just by putting a screw driver's metal rod across two terminals on (what I guess was) the starter solenoid, next to the battery; is that right? Only method I knew involved pulling plug from ignition and sticking a wire in two holes.

you need to jump the ignition or it will not allow the bike to start. jumping at the solenoid only bypasses the start button not the ignition switch.

I moved all keyed parts on my 86 from one bike to the other, it was all nuts, bolts, and plugs. Not too hard. I did disconnect the battery ground before doing this.