I've used molasses in HP. It does increase lather. It also gives a lovely rootbeer brown color to the soap. If you use enough, the lather will also be brown, but does not stain. It gives a faint sweet scent to the soap, as well.
Do be mindful that molasses will heat up your batter even faster than honey. That's not a big problem in low temp hot process, but in high temp hot process, be ready to remove the pot from heat and stir down the volcanos.