2) In theory new hardware can seem to work with a simple PCI ID
update, and later we find it needs extra quirk handling or specific
driver support. This could mean adding buggy support for new hardware
to -stable. In practice, hopefully this isn't a real issue.
3) It hasn't been a pressing issue brought to our attention until this
thread and its predecessor earlier in the month.
My own personal experience is each time I've needed a PCI ID update for
new hardware it's also needed changes to the driver (read: e1000, every
single time). So from my perspective neither sysfs nor relaxing -stable
rules slightly would actually help provide support for new hardware,
but that's clearly limited experience.