Another issue is that it’s not easy to handle 4 individual pieces of luggage
The bottom line is: panniers are acceptable on the bike, but a PITA off the bike.
I altered my own pair of Ortlieb Sport packers, when I got my Bike Friday, and it's particular front rack.
2 strips of webbing, went under the top rail, pierced by the screws that hold the bag together.
pair them together ..
Not as good as the Brompton system.. 1 bag frame clip,
but having the handle straps inter-woven to be one , and up, out of the wheel
works..
Touring kit for the Brompton, Big Bag on the front of the frame,
and a Carry Freedom City, bike trailer .
Cascades design Portage pack modified to go in the trailer, dry-bag.
instead of the standard sling hammock bag.