I know you can get 2mb chip in an A500, it's just not as easy or as cheap as buying an A500+ with an A501+ fitted though. As far as I know, I think your Supraram needs to be kept installed now you've cut those traces, or solder some switches to them so you can turn them mod on/off.
The ACA500 can use the 512kb trapdoor ram as chip without any modification to your board!
Academy 500
It's ACA, stands for
Amiga
Classic
Accelerator.