You can do what you want but almost nobody puts dual handsets on a spirit or sidewinder. So this is kind of weird. A handset and a nerd is possible, but 2 petrels, no.If I was buying new, I would put at least 2x petrels with 4-pin cables on there and the foam coating which brings you to $9k for the new unit. You will most likely not find the 4-pin cables on any used units, so keep that in mind.
Replacing the splitters is totally unnecessary unless they have failed - despite them being the massive weak link in the spirit/sidewinder heads
I would agree that this unit is not at all what I would recommend