The reskin files are exchangable as they only show what is available to select through the menu.
A reskin with almost all emulations looks like this:
36-XL LIVE;36-XL LIVE;slf-Self;17-Rider;34-ONE;35-XL;37-GO x50;39-Start;18-GO x20;25-GO x30;24-GO x40
In this example the XL Live Emulation the default one.
To have the x30 Emu it should look like this:
25-GO x30;25-GO x30;36-XL LIVE;slf-Self;17-Rider;34-ONE;35-XL;37-GO x50;39-Start;18-GO x20;24-GO x40