I'm typing this from a laptop running Linux, because AFAIK, NetBSD
simply cannot do what I need on that machine.

I think following some PCMCIA model that allows hot-swapping is a
great idea.  The linux dameons suppport that, and David Hinds seems
to do a great job at supporting them. 

I don't know that much about Stefan Grefen's PCMCIA support, but I
have understood it correctly, it doesn't support hot-swapping.
I see hot-swapping as a non-negotiable item.

I've suggested following a Linux-style model before. The responses I
got would make sense if they'd come from someone who had never
actually *used* PCMCIA cards, or had to swap them, or believed that
problems with interrupts from `stopped' cards, or in the midst of a
hot swap, were somehow insurmountable.   I just swapped cards,
and as a rule, it seems to work for me :).

One problem with hot-swapping on a Linux machine (e.g., between
Ethernet-like interfaces, say wavelan and 10baseT) is that removing an
ethernet card causes the interface to go down, which (on Linux) causes
its inet address and routes to go away.  Any process that sends a
packet during the out-time gets an ICMP unreachable and dies. 

I think it'd be really, really, great if NetBSD could support
hot-swapping PCMCIA interfaces without killing TCP connections during
the swap.