Hello, I'd like to mention one other solution:
1. Open an empty family of the same catagory.
(step 2. has 2 options, pick either 2a or 2b)
2a. Create a ref. plane in the unhosted (parent) family. You could even use the standard ref. planes that are present in a new family.
OR
2b. Draw a small extrusion from Ref view, at your origin point (ae 1 * 10 * 10),
and make sure you disable the 'visible' parameter.

3. Insert the Fase Based family into the new family, and place it while in the 3D view on the plane / fase you need
(use the face you need, a.e. for ceiling mounted stuff you use the underside, floormounted, use the top, upright-position, use the front or side)
4. Re-allign the nested fase based family to the origin point
(this is the crosspoint of the ref. level, and 2 ref planes which have the 'Defines origin' parameter set to true)
If you want your nested family to be offset by some amount, you can move the nested family to that position.
4b. If you need to move in the 3th axis, move the ref.plane / extrusion (or create another at the disired location and re-host the nested family.

(image example: Fase based lighting fixture family placed on the small extrusion)
5. Save the family
Done!
Now you can insert the family in a project, unhosted.

Extra's:
Optional 1:
Copy the parameters, variables, and all you want for functionallity, to your liking, to the new family.
(if you're making your own family from your own fb family, you could use shared parameters)
Optional 1b:
Add types, and type parameter for the family type of the nested family.
This way you can still use the different types that the face based family has.
Optional 2:
Delete the ref. plane / extrusion you placed the fase-based family on (within the parent family). The nested face-based family won't need it anymore.
/!\Important note:
I'd reccommend to only deleting it if it causes you problems.
Deleting the host makes it so you can only move the nested family in the 2 dimentions of the plane / face the family was placed on. The ref plane / extrusion can be moved withing the parent-family, to move the nested family in the 3th axis. As long as you make sure you disable the visible parameter of the extrusion, deleting it shouldn't be necessary in most cases.