I know you said you don't want to redo the floors, but if you copy and paste a floor into the same place, and then edit the boundary of each floor, you can remove what you don't need from both floor footprints, leaving you with two separate floors without 'redoing' the floors. then you could switch one to a different floor type...
Parts are great, but they add complexity that sometimes isn't warranted.
OR, you could also take the main floor type and remove the finish from the floor. keep just the main structure element and subfloor, if it will be consistent over the whole plan. Then, you just edit smaller finish floor elements in specific areas. it's still more work than having one big floor, but splitting and painting, or making parts is also work, so it depends on your speed at these different types of work.