I've been reading up on the issue of hot plugging but i haven't found anything conclusive, like i guess esd could have an effect it you physically insert the mini din plug into the mac while on, and it the key tab is broken in theory it might be possible to short out the 5v to ground of the data pin (ill have to check this further though), most makes are fused on the 5v line though so grounding that wouldn't be the end of the world.
I read the chapter on ADB in Apple's book last year while troubleshooting one of my SE/30s that didn't have a working mouse. I don't completely remember what it said about hot swapping, but as far as I can tell, If you are doing the switching with something like a microcontroller, the wires themselves will never actually get physically disconnected. The computers would just think that the signal has stopped momentarily, in other words, think that you have just gotten up from the computer. This would minimize the ESD threat at least. You could probably put something quick together using a few mini-din sockets, tact switches, and a $5 Arduino style board.
I've yet to see anything conclusive on the matter. Given the prevalence of rotary switch based KVM solutions from the day makes me think that approach is fine. A manufacturer, opening themselves up to the possibility litigation over wrecking one or several Macs, K, V & M would have been a serious event. So I doubt that an electronic switching solution is really necessary.
Hot swapping is defined as unplugging and re-plugging active peripheral in hot sockets of powered computers. KVM rotary switching is decidedly not the same thing. Any fumble fingered attempt at hot plugging cables runs the chance of damage, but many of us have hot-plugged ADB numerous times without bad things happening.
I always kept an alias of ADB Reset on the desktop of my KVM'd Macs so I could Tab to it to hit enter, running it from the KBD. That done, all was well again in the world of ADB had the mouse lost its place.
It's easy to find two way printer switchboxes with the pushbutton switches like this Black Box Mac KVM, such have plenty of contacts
View attachment 26081
In these days of inexpensive 10x10cm PCBs, maybe do a modular setup of vertical connector boards plugged into chassis components servicing any number of cascaded hookups?
I like the notion of re-purposing unused (in Mac KVM switching) lines an HD15 switchbox for ADB. I also like building octopus cables. Stick a hub in the box and add unswitched Cat-5 to each.
Pin
Name
Dir
Description
1
RED
Red Video (75 ohm, 0.7 V p-p)
2
GREEN
Green Video (75 ohm, 0.7 V p-p)
3
BLUE
Blue Video (75 ohm, 0.7 V p-p)
4
RES
RESERVED
5
SGND
Ground
6
RGND
Red Ground
7
GGND
Green Ground
8
BGND
Blue Ground
9
KEY
-
Key (No pin) / Optional +5V output from graphics card
10
GND
Sync Ground
11
ID0
Monitor ID Bit 0 (optional)
12
SDA
I2C bidirectional data line
13
HSYNC or CSYNC
Horizontal Sync (or Composite Sync)
14
VSYNC
Vertical Sync which works also as data clock
15
SCL
I2C data clock in DDC2, Monitor ID3 in DDC1