Self leveling cement over Tile Thin-set?

I'm in the process of redoing the floor in our guest bath and I'm ripping up the old floor tile. Thing is that I'm left with a bunch of thin-set on the hardiboard that the previous owner used. Can I simply use self leveling concrete/cement to fill all the voids and get me back to a flat surface, rather than having to remove all the old thin-set - a painful and almost impossible job. The hardiboard has also been laid down with thin-set, so it's a real pain to remove back to the subfloor.

I'm thinking a 1/4 inch or so layer of self leveling concrete will get me back to a level sound surface and all I'll need to do is somehow block off the air register and the toilet drain so they don't "fill" with the leveling cement. I also plan to hold back the cement from the tub sides so that as it dries it won't crack my tub - is this necessary?

Any help/advice would be greatly appreciated.

Thanks, boostnet. Yes, I did a little more research and asking at HD and I've got the primer and leveling cement to start work tomorrow. If I had the money, I'd go with the electric heating, bu this is only the guest bath (kids bath once they are older) and it gets used very infrequently.

Thanks again.