So don't laugh, I'm of a mind to get a Commodore 64 keyboard and turn it into a USB one. And I'm wondering about how I should treat some keys, and I'd love to hear some suggestions.
This is the layout. After that come some jumbled thoughts I've had so far. I know they're leaning towards tl;dr material, so feel free to give suggestions without reading the rest of this post.

One thing I could do in theory is try to match every key's original function to something as close to it as possible, but this would not be practical.
There's a text key to the left of 1. I could make this act as Escape instead of tilde/backtick.
There are three text keys to the right of 7890, three to the right of UIOP, and three to the right of HJKL. I could make two of each threesome work like the keys in that position on modern keyboards. I'd swap at least the + and - keycaps, maybe some others. (I could in theory try to match the ;[;] keys to what they're marked as, but I'm leaning away from it - sounds like unnecessary hassle.)
That leaves three unused text keys on the right side. One would become the backslash, and another maybe the 102nd key, no idea what to do with the third.
I absolutely need a Tab key, and I'm not sure if I should make Stop do it, or make Control into Tab and Stop into Control.
The Delete key actually deleted to the left on the original, and it's in the right position for a Backspace, so I think that's what it should do. The Home key right next to it could reasonably stay Home, I'm just not sure how to do End (maybe put it on one of the unused text keys). An alternative is to have the two keys in the corner be "delete left" (ie. Backspace) and "delete right" (ie. Delete).
The two cursor keys on the C64 work as down and right, and with Shift they become up and left. This isn't nearly as clumsy as it sounds, but the problem is that shift+arrows already has a different meaning in today's software, so I'm thinking of a cheat: I could make the right Shift just be Shift, except when it's used with cursor keys, where I'm going to send the signal that "shift is no longer pressed, but an up or left arrow is". And when I actually want to use Shift together with arrows, the left Shift could do it.
This is making me think I could just generally make the right Shift (or some other key) into a "Fn" key of sorts, combining with non-text keys: Fn+Home = End and so on. That would also make it easier to squeeze PgUp and PgDn in there somewhere.
The F1-F8 could be used as labelled, but I could also make them something else (Home, End, PgUp…) and just press Fn+1 for F1 and the like.
The Commodore key could be Alt. I'm not sure I need a GUI key at all unless I decide to use this keyboard with a Mac. It would be esthetically pleasing to have Commodore as the Fn key, but I'm afraid it's physically far from other keys I'd combine it most with, so it would be impractical. It also wouldn't be bad to have some key for Alt Graphic.
This leaves two keys unaccounted for:
Restore is wired completely separately from the rest of the keyboard, so it has super Ghostbusters powers. But it's in an awkward spot to be used as a modifier. I dunno. Maybe make that the general Fn key, just keep the Fn functionality of the right shift for cursor keys.
Shift Lock is hard-wired parallel to the left Shift, but I think it's easy enough to separate. It's probably not easy at all (for me) to make it into a non-locking key. So what good is a physically locking key? Caps Lock, for the lulz? (I know there's a separate USB HID code for a physically locking Caps Lock.)