my upstairs toilet started to leak (water was leaking out of lights on
ground floor), so i pulled it up and it looks like i need to re-install some
octagonal tile; put on a new wax ring an then re-seat the toilet. the
toilet had been rocking side to side, but i'm not sure exactly where the
water was coming out of, but it looks like it just needs a reinstall.

but...

when the toilet was installed whomever installed it cracked up some old tile
to fill in the voids around the octagonal tile and the round flange. it
looks like he just adhered those pieces in a bed of tile adhesive or grout
ontop of some substrate.. the top of the flange is about 1/4 inch higher
than the floor.

rather than try to piece together what was there, i thought i'd relay the
tile and then fill in the void with something like Bondo (fiberglass resin
autobody filler). the stuff hardens quickly and can be made level with just
a putty knife. i'd say there are areas of up to 1" between the edge of the
tile and the flange.

good idea or is there something else i should consider? thanks in advance