The D180 does not follow vertical guidance (glideslope) - none of the Dynon legacy products do. Localizer, yes, glideslope, no.
Carlos - I think you're missing a valuable piece of the "big picture how does it work" view.
The EFIS IS the autopilot controller. Not the servos - they're dumb, they just crank in as much control input as the autopilot controller tells them to crank in. NOBODY makes an autopilot servo that has all the smarts of a built-in autopilot controller.
Also, in the experimental world, nobody really makes a stand-alone modern autopilot that will handle the VOR-ILS signals to steer the airplane. There's a reason for this. To steer the airplane the autopilot needs to know a BUNCH of information in addition to the VOR-ILS data. For instance, it needs to know which side of the airplane is up - it needs attitude information. It also needs to know which way it's pointed - heading information, or, even better, track information.
I know your intent is to produce a simple "like the old days" autopilot. Those are available. The guys in the certified world are yanking them out as quick as they can in favor of modern, digital autopilots. Why? Because those modern, digital autopilots do SO much more than their "steam" predecessors, and do it SO much better.
If your desire is to have a stand-alone autopilot, I would counsel you to consider installing a device like the GRT Mini-AP or Garmin G5. Yeah, sure, they are EFIS devices. Just program your brain to think they are a dedicated autopilot controller, with all the EFIS stuff there as a fancy backup to whatever other "primary" flight instrument you opt to have in your panel, like the D180. By going this route you will open up the opportunity to add at some time in the future a GPS navigator that uses ARINC 429 signalling to do all the REALLY neat stuff like LPV approaches.
Or, just stick with your D180 and accept that it's the brains of your autopilot. Many people have gone this route and found it works very, very well, save for having to hand fly the vertical portion of the ILS.