Hi Dikki
The vast majority of arrangers are sold to home uses, which is why a lot of the features you say should be removed, are fitted. (Home uses utilize them)
The reason hardware arrangers have slow ram and USB is because it takes typically 2 years to get from prototype to production, so the technology used is usually about 2 years old when the product is released, as an example when the prototype Tyros 2 was being tested, the mainstream computers were P3 with PC133 memory and USB 1.1, and this is why Tyros 2 uses PC133 Ram and only has USB 1.1.
All Wersi instruments up to 2003 used P3, PC133 and USB 1.1, however due to the fact that inside they are just normal computers, it was easy for Wersi (And existing owners) to fit P4 boards with DDR memory and USB 2. (This is what is meant when Wersi say there instruments are totally updatable)
Enjoy whatever you play

Bill