Can you elaborated further as to what you mean by your statement, 'it lacks lather'? In other words, do mean that it lacks bubbly lather or that it lacks creamy lather?
I ask, because 'on paper', it looks like your formula would be super bubbly, but I've sometimes found that having lots of bubbles does not always equate to having 'great lather', because it's lacking somewhat in depth, or 'body' or 'oomph'. The best way I can describe it is like the difference between having 2-dimensional lather and having 3-dimensional lather.
If it's depth/body/oomph you're looking for to enhance your bubbly lather, if it were me, I'd switch out your palm for lard. Besides lard, other ingredients that I've found to be lovely 'depth' enhancers are castor, goat milk, coconut milk, and sodium lactate. I've found that by just subbing as little 30% goat milk or coconut milk for part of one's water amount lends a nice creamy depth/oomph to the bubbly lather already present.
What type of water do you have? I ask because hard water can really mess with one's bubbly lather. I myself have pretty hard water, and I've found that adding a little of the chelator Tetrasodium EDTA to my batches (@ .5% of my entire batch weight) helps my lather out quite nicely. In lieu of EDTA, you can use sodium citrate instead (does the same thing).
Like the others have said, you can use sugar to boost your bubbly lather quotient. I myself like to use 2 tablespoons ppo in my batches. Of course, you'll have to play around with it to find the 'sweet spot' amount that works for your own formula, but for what it's worth, that's the amount that works for me.
IrishLass