I see from the manual the V1 only provides zone 2 pre-outs, and hence needs an external amp. Since all the newer models (even relatively cheap ones) have the option of using internal amps for zone 2, it's pretty likely that the V1 just doesn't have the hardware to assign amps to zone 2.
If Receiver Manager could unlock any new capability, we should see those commands in the RS-232 doc for the V1. Although in fact RM for any given model typically only implements the officially supported features, and if there were any extra capabilities you'd need to send the RS-232 commands from a custom application. (This is what I managed to do with the 1800 to manually adjust the parametric EQ -- that feature is not available through the GUI or through RM, but the RS-232 codes were documented and they worked.)
As for firmware mods, I know from experience with my 1800 that they take a lot of time and effort. But if you find the service manual for the V1 it will at least tell you if the hardware is present.
I suppose you want zone 2 to play at the same time as the main zone? If not, maybe you could connect your zone 2 speakers to the main speaker B terminals, then use the A/B switch to select either main zone or zone 2?Edit:
I found the RX-V1 service manual here
. A quick look at the block diagram shows that zone 2 is implemented simply by selecting one of the analog inputs and feeding it directly to the pre-outs with only a volume control along the way. So unfortunately I think only a hardware mod would allow you to feed the zone 2 source through unused internal amps.