Brompton owners

Why bother removing the derailier? Just don't use it! The shift is ok once you get the hang of it.

Weight

If you're at all competent as a mechanic, just buy a new 2 speed rear wheel and store the hub gear in the garage until you have to return the bike. Take off the 3 speed shifter and the rack and you've got an S2L that you can change back easily.

In terms of the rack issue, I prefer to carry everything in the S bag on the front block, as you can fold the bike completely with it still attached, as opposed to taking everything off the rack to have to fold it.

S bag is a must when I can afford it.