Lovely. There are lots of peripherals from around the same time that I wish were as programmable as the 1541, or even just a little bit. For example, if you'd been able to send, say, 50 bytes of 8085 code to the VT-100, and use a 30-character buffer, you could have handled backspace locally in the terminal, both improving responsiveness and dramatically lowering load on your VAX back in the days when handling an I/O interrupt to echo a character was a substantial load. If the VT-100 or H19 had had 20 bytes of SRAM mapped into its font ROM space, you could have had four programmable glyphs — enough to display a pixel-positioned mouse pointer on top of the text, or really dramatically spice up a lot of video games of the time. (You'd probably want to download code into the terminal to make the animation smooth, although 9600 baud could have gone past 30fps.)
And of course today we have junk heaps full of TVs, calculators, and feature phones that people are throwing out basically because they don't have any way to reprogram them into something useful.
The keyboards on some of the Amiga's had a SoC version of the 6502 (it's a model with a tiny PROM an some RAM and a few IO lines). Unfortunately not reprogrammable like the 1541.
I used to freak out PC users by explaining how my Amiga 2000 had a M68000, but with a M68020 accelerator board, a PC bridge board, with a 286 accelerator (the A2000 with bridge board could run the PC board "in a window"). On top of those CPU's, it also had a SCSI controller with a Z80, and aforementioned 6502 compatible CPU on the keyboard. Now that's multi-processing :D (Of course the M68000 and x86 were disabled).
If you had a reprogrammable 6502 in your keyboard with a few hundred bytes of RAM, what would you use it for? Keyboard macros are one possibility. Or you could encrypt the keyboard-computer connection. Maybe some games would benefit from a "rapid repeat" key that let you send a single key or keyboard macro at 100Hz?
I've been saying that for years, and of course there are people in some places already mining them, but I can't help but feel that it's terribly stupid to melt down and re-smelt a cellphone just because you can't figure out how to reprogram it. The cellphone is worth a lot more than its constituent raw materials.
And of course today we have junk heaps full of TVs, calculators, and feature phones that people are throwing out basically because they don't have any way to reprogram them into something useful.