The X100 has a 49mm thread via a AR-X100 adapter. The Olympus TCON-17X has 55mm threads, so the connection should be no problem. Has anyone tried it?
The only way to know what will happen is to try it. As you state, "the connection should be no problem", just use a 49-55 step-up ring. However, the lens is 23mm, so the ring may be visible along the edges of the frame.
Step-up rings are fairly inexpensive, so if you already have the adapter and converter, you can go ahead and try it. Otherwise, consider you'll likely have a much better experience by using FujiFilm's native converters:
- Wide Conversion Lens WCL-X100 II - 0.8×, 23mm → 19 mm
- Tele Conversion Lens TCL-X100 II - 1.4×, 23mm → 33 mm