Haven't quite gotten Army Ants to work, but if you're talking about Leafcutter Medias, I have gotten them to work. Really, all I did was copy over some code from the "Extremis" level's save and thus obtained the ants it contained, lol.
Ha an interesting approach. The colony setup is just a big structure that is saved into the save file so yes it should work fine in freeplay. Interesting that this works. Army ants are not in extremis so I am nut surprised they don't work
I opened the file "ExtremeHoldOutProgress.sav", then copied the code from there into "Colony7.sav" (the save file for my seventh Formicarium colony). You have to copy just a few specific lines of code, or it'll break your save. Until I can write an exact guide, you guys should use trial and error, with a lot of backups, lol. Don't edit your saves without them. Ofc, that's kind-of common knowledge, so I'm not really concerned that you guys won't use backups, but just in case. Anyway, have a good day!