That Playxpert is probably your best bet. Personally I only use dual monitors for games like FSX and Supreme Commander, which natively support it. The main reason I don't use it more often is exactly what you're trying to get around; the game dropping out full-screen.
Separate controls for a VM might be posible if you disable one set in a hardware config on one machine and disable the other set in hardware config on VM. Same for monitor output. But if you have to task switch to the VM like you said you're back at square one.
As far as I can find info on it, it's not something anyone has a solution to.
