Go ahead and try it, but I think you're misunderstanding just what it means to do all that gender and race bending. I looked at the X-arcade and did only a small amount of research to understand the basics of how it works. I lost interest in purchasing it so I never bothered with the fine details.
The short of it, it's going to take a few more adapters than what you've got because you're probably going to need to interpret the protocol at each stage. In the end, you're going to spend too much money trying to get everything to work together when going with a different solution might net you more satisfactory results.
The long of it is; The X-Arcade obviously serializes the button presses. XGaming claims the XA, "Uses standard serial connection." I've yet to see anyone report plugging in the X-arcade into their legacy serial port and getting results. Because of the included PS/2 adapter one can probably assume it's just a DB9 to a PS/2 cable. That likely indicates the XA can natively communicate via PS/2.
Here's the gotcha though. The XA uses a box for the USB adapter. It's hard to get a good photo the insides, but it looks like there's a circuit board inside. Likely means the XA can't natively communicate via USB. That's the ingeniouseness behind what XA is doing. Rather than modifying the firmware with each new console, they simply sell the updated controller in a seperate box. There's ZERO need to provide support to update existing XA's in the field with a new protocol and a way to charge the customer extra if they desire the new protocol.
I lost track of what you're trying to do, but in the end you're likely going to encounter protocol problems.
You're giving the XA a Serial<->PS/2 adapter, so now it's communicating in PS/2 to the KVM. From the KVM, you're switching from PS/2<->Serial to go to the individual console adapters. Ooops.... The XA is communicating in PS/2 to the KVM which is also a PS/2. The KVM is sending out a PS/2 protocol, not the RS-232 protocol. The XA probably has no idea it's connected to a console adapter down the line. To consider a possibility of working, you'll need a box (not a cable) that actively converts the protocol from PS/2 to RS-232. This assumes the serial protocol is standard RS-232.
The USB presents the same problem. You can't just use a passive PS/2 to USB cable from the KVM (unless the KVM can actively convert to the USB protocol). You need an active PS/2 to USB converter for that. You can forget about a passive Serial to USB cable, it's going to have to be active.
With all these conversions, you're going to encounter some interesting limitations. Can you ensure that all the active converters at each stage will pass all the key presses or is one of them going to restrict keypresses at some point? What about lost packets? Packet delay? Those protocol conversions aren't free you know.
My suggestion? Forgo the KVM entirely. Use a dumb 1-to-X Serial selector box. Most use those annoying selector knobs, I've seen a few circuit projects that use a digital selector switch. By doing so, you cut out half of your conversion problems. With a little circuit bending, you might even be able to adapt a video selector switch for the consoles as well. I suspect that's the main reason you're doing all this contorting with the KVM. By using a dumb 1-to-x selector, you minimize the number of active protocol conversions required.
A PC can accept multiple USB keyboards, so a direct connection from the IPac to PC will should cause no problems.