Yes you can use USB on a stock A2000 using the PD stack, you can add a ZII Clockport for 50 something. There are Clockport adapters on Amigakit. You can wait for an inexpensive Thylacine card or buy one that pops up so often. The Subway is really meant for the A1200. There are Algor and Highway cards out there. The Deneb is pure genius.
As to the need or usefulness of USB on an Amiga, you will always hear the squeaky wheel; nothing is ever right with them, they will complain about anything and everything to appear smart or clever.