Replying to feipoa's PM.
Predator99's idea of using a separate card to load a SCSI option ROM seems possible, if you'll manage to properly execute it from a NIC, then it'd be the safest method of BIOS "patch".
Horun is right about the location of the AIC-7880's option ROM image, except it starts precisely at 48000H and ends at 4FFFFH (32KB).
The two latest firmware updates for the standalone 2940UW card - ver. 1.34.1 and 2.20.0 (36KB and 41KB respectively) are already larger than the reserved space for AIC-7880's option ROM in the NEC's BIOS, thus it wouldn't be such a simple task to patch BIOS with larger images, using only a HEX editor w/o messing it up completely (no Phoenix BIOS editor that I found, could recognise NEC's BIOS). It's possible to relocate other option ROMs to different addresses and make enough room for larger AIC-7880's images, but I wouldn't reccomend experimenting with a motherboard in a way which could easily brick it.
I took a slightly different approach of patching system BIOS, instead of risking to corrupt original BIOS image with non-standard sized ROMs, I had extracted AIC-7880's option ROM from Asus P2L97-DS mainboard's BIOS, ver. 1001. It's exactly 32KB in size and seems to be of 1.32 version (according to the option ROM's name), though I'm not entirely sure if that's the case, there's no mention of its version anywhere in the image. New option ROM was inserted into 48000-50000H 48000-4FFFFH range, 8 bit checksum is 0.
Attaching modded NEC Proserva V BIOS (ver. 1.00.14) with some extracted option ROMs for AIC-7880.
EXPERIMENT AT YOUR OWN RISK.
*Edit: next option ROM starts at 50000H, it's just a typo, BIOS is patched correctly 😉