It cannot be done; not presently, and since there are no non-Task Force missions I'm aware of like that live, probably not for a while.
If we get the ability to create/edit our own maps, there are several tricks that could be used. In the meantime, the only way you're going to be able to manage it is to set up another mission in the arc with the other map. =/ Pretty kludgy, but them's the breaks. You might want to just write down your idea for the arc somewhere and wait for the MA toolkit to mature.
There are a number of maps available with two different styles - the ones I know about are the office map that turns into smooth caves. I think the sewer/caves are also available as well. That's as close as they come right now.
<《 New Colchis / Guides / Mission Architect 》>
"At what point do we say, 'You're mucking with our myths'?" - Harlan Ellison
The idea is an invasion from another dimension that Portal Corps doesn't have access to, so the players would have to do several missions to figure out what is going on and then one to find the portal and enter it kind of like Hero One's Team had to do during the First Rikti War.
I have an idea for a mission arc, but it would require the player(s) to go through a portal in the mission which would take them to a different map.
An Example....You are doing a mission in an Atlas Park map and find a portal which takes you to the future/alternate reality version of Atlas where are the buildings are destroyed and inhabited by the living dead.
Can this be done?
If not, what would be a god work around? I would love to be able to do it within a map, but if it can't be done....