It wouldn't hurt or maybe it would? To experiment. I myself find that cacti, succulents respond well to soluble fertilizers Traditional mineral cacti mixes are pumice and pine bark, or pumice, peat, and pine bark.. They work well with other succulents too. I have been experimenting with coir too, seems like a nice product. Lasts longer than peat. But is neutral which is great in some cases, not so great in others. Plants that come form desert regions really do not respond well to any compost, as it is not in the environment. Also plants that come from sandy soils same thing. Some tropical succulents will like the compost.

The gritty mix would probably work well with some succulents. Bigger cacti require very dry soil most of the time, and the gritty mix can get dry fast, so is a good choice. I myself don't like it for some plants like fruit trees, but any gardener that pays attention can grow plants in anything.
If you decide to use compost, go light on it, as it tends to stay wet a long time, it doesn't drain well either. Be careful not to over water.

RE: "First off I'm using 1 part Red wood fines (Kellogg's big R) and 2 parts Pumice."

Maybe I'm an OCD purist but at what point is Gritty no longer entitled to be called Al's Gritty(tm)?

The above may be a kind of gritty derivative but it's not Al's recipe. And I believe it's a disservice and confusing to call it as such.