My DSM is located in my dining room, and there is a carpet under the table. Threads migrate all over the house from the carpet! Thread hitchhikes on my shoes...
Laminate flooring or a ceramic tile would work well. The tile will not scuff or get marked up by rolling furniture. You can get tile that is 12+" square, so can set the frame for the long arm level.
I would also suggest the insulation and radiant heat if you're on a slab. If your budget won't allow radiant heat in the entire room, then put it where you will situate your DSM, cutting table and where your long arm will be. Warm feet make the sewing experience so much more pleasant!