What Creavion said.
Maps which use directly the XPickups pack, are just like the RX maps that use additional mods like BPak.
Some of these maps don't use the XPickups features at all, and in this case, you have to ask those maps owners if they are willing to make a version of their maps without XPickups, but other maps use some of the new features that don't even exist in the standard UT (like Creavion said), like triggering, weapon lockers, new pickups and wildcards, there's no way to take out the XPickups from there, otherwise the original gameplay idea will be broken, or in the worse case, certain sections of the map would have to be remade, simple as that.
I can add more support for arenas (apparently, only the ammo isn't replaced by some weird reason
), but other than that, you would have to ask the mappers to take off that pack from their maps, and personally I think almost no one will have that trouble (and since the problems are downloads, don't forget that some maps have more than 20M of filesize).
But you can try to PM each map owner and ask, but I don't know what their answers are gonna be, since that's no longer in my hands.