Ok, this is the solution to the problem.
1. We need to place a line somehow in the middle of the wall (any configuration) in plan and possibly in section. In section we also might have a line in the middle of slab and roof. It must be line, not symbol fill, to avoid problems exporting drawing to DWG. I guess AutoCAD can have fire rated lines already in standard settings - let say in AutoCAD Architecture. If yes - match these lines with ArchiCAD lines in translator.
2. We can use automatic placement of labels - when selecting all walls on plan and use command 'Label Selected Elements'. In USA version this command even placed as a button on top strip of standard toolbar. In INT version hidden somewhere in Document menu. Don't recall where exactly.
3. Label knows its XY location to project origin: LABEL_POSITION
4. Label also knows position of the wall, length and rotation angle: WALL_POSITION, WALL_DIRECTION, WALL_THICKNESS and another details as radius of curved wall.
5. Label can read property of the wall and receive fire rating value.
6. Quite simple to figure out on plan position of the line in the middle of the wall and choose right line-type for different fire-rating value. Labels can be placed in separate layer shown on fire strategy plans only.
7. A little bit more complicated in section. X position on screen can be problematic to detect automatically, but at least we can know exact Y (wall height). Same with slabs - X coordinate for slab then can be adjusted manually. But sections with fire rating is not needed so often, so it's manageable.
I can create such labels. And upload to this forum and BIM components.
Beer please.