That all makes sense to me. I totally understand that they need to go after the models that will generate the sales and some of the common birds like PA28 have been dominated by Trutrak already so maybe they figure that is a lost segment? Ether way I am super happy with my HDX system - it is just amazing. The certified aircraft world definitely has its drawbacks. After I dont need the hauling capacity of the 6 I'd love to think about building an RV....It's understandable that Dynon is using it's engineering resources to do the design work on the types with the highest numbers of possible sales. The frustrating thing is that the experimental version of the autopilot can be pretty much installed on any thing a builder builds so long as they don't mind making their own mounts and control rigging.
I suppose the FAA is putting Dynon through a lot more hoops than common sense would dictate. As far as I know Dynon's autopilots haven't caused a lot of problems for all the experimental types they've been installed on. Unless the physics works differently for aircraft that fly using experimental certificates vs. type certificates. A lot of time spent doing proofs does not seem to be warranted. There are conceivably type designs that exhibit flight properties that might not be safe to fly with an autopilot. I don't know of any TC'd aircraft that are in that category since they would probably not get TC'd because it would be hard for a human to fly them as well.
The other thing that probably slows Dynon down is that they feel like they need to have all the installation parts (mounts and rigging parts) developed and on the shelf before they add a type to the AML. That isn't an FAA requirement. It's fairly common that low volume STC's installation designs that require the A&P to fabricate sheet metal parts like brackets. Most of the rest of it could be solved by calling out standard AN parts.
The only way Dynon is going to make a significant dent in their backlog is to hire an engineer to collaborate with type clubs or other type owner groups to develop designs and approved data and walk it through the FAA. Dynon could charge the groups for the engineer's time collaborating with the outside groups. As part of the contract for that collaboration, the resulting design and data could be signed over to Dynon.
A side benefit of that to Dynon would be that they would be getting their engineering underwritten by groups of owners that are willing to put their resources (read time and money) into the process and are likely to actually result in system sales. That takes it out of the realm of a market projection committing a lot of company time and money.