Warranty is two years, right.
128MB is possible from a PCB point of view only on the AC1230. However, the memory is not user-upgradable. Since we're doing quite some memory shuffling, the $c0 mem and kickstart/MapROM area need to be in a fixed place at the end of the memory chunk, therefore the CPLD program must be adapted if more memory shall be installed.
I really don't get it why you want all this memory, as a WHDload machine is perfectly happy with 32 megs. Just one or two games make use of roughly 40megs using pre-load, and these work great with the 64 megs that are included with every ACA1230.
The memory chips on the ACA1230 are special - they are 200MHz types that are not widely available. These are brand new Winbond types that only became available in summer of this year. We were the first in Europe who had them, and we're putting the tight timing possibilities to good use, even though the memory controller runs at 56MHz only (also on the 28MHz cards!). Even if memory would be user-upgradable, you would not be able to buy the chips anywhere.