We already have this, a full DG with an HSI. If you have firmware from the last 18 months or so, you should have this option.
But I assume you mean a full compass rose on top of the attitude indicator.
We're totally thrilled that our customers have ideas to make our products better, and we do listen to all of them. In this case, we have actually looked at doing this, many years ago, and even have some code to do it. The problem with it is that it is a human factors disaster. Things all over the screen, rotating in one direction while the horizon goes the other way. The roll scale ends up inside this other circle and you have pointers everywhere. On top of that, the screen just ends up totally cluttered.
It just really isn't a safe thing to do. If you look at all the certified units on the planet, none of them do this, and there's a good reason for it. We take the usability of our products very seriously, and this type of display just doesn't mesh well with usability.