Switching to isomalt will drop ~50% in the caloric content, but change mouth feel and water retention a lot. A different confection will be the result.
Yep. Adding another lower/zero-calorific sugar but with a positive heat of dissolution (to counter the negative one of isomalt) can really help here.
Similarly, you can choose sugar pairs to promote or suppress crystallisation, as the recipe style requires. This is done by selecting sugars with similar or dissimilar molecular geometry and charge distribution.
Why not erythritol? Isomalt can cause some pretty severe gut issues (to which I can personally attest, unfortunately!). It's also still quite calorific (that is, it is metabolised) - erythritol isn't. I can eat it in high quantities to seemingly zero consequence. It's also got an entertaining mouthfeel, where it cools the mouth; so does isomalt, incidentally, but it's not nearly as noticeable.
I have done quite a bit of cooking with erythritol, simply swapping sugar out for it, and it usually works great. Erythritol is only about 70% as sweet, so it can sometimes be necessary to adjust for that, but really, most things are already overly sugary, so it's usually unnecessary.
