I'd vote no for Cardies replacing Maquis in the actual show. But having that happen in a Myriad Universe story or having Gul Evek and his ship turn up in a two parter like "Equinox" would have been pretty cool. Or have it work something like the Hirogen episodes where you meet them in one episode, encounter them a bit later and then several seasons later catch up with them again. I think Evek would be great as a foil to Janeway in that Richard Poe would be a great actor for Mulgrew to bounce off but also in that unlike Ransom or even Chakotay Evek isn't bound by the same code of ethics that Janeway is, but also doesn't need to be a mustache twirling villain. Also you could throw Seska into the mix and have her try to manipulate both ships. Could have been fun.