is AR in software
Space is tight in the ACA500 firmware, even with two kickstarts+menu+devices+utilities compressed to 512K! There is certainly not 136K of space available...
If you really want it in ROM and not as software, your best chance is to make a large custom Kickstart ROM for your machine. Some have added scsi.device and utilities to kick 3.1, for example. Then you set ACA500 to boot from On-Board ROM, and it will work and boot from your custom Kickstart ROM.