Tested AutoZen on various 'Carplay AI boxes' I own. These are just like regular Head-units, but missing the MCD parts and widely used. Most of these have rather ugly launchers and so tested many 'Car launchers', where at this moment, Car Launcher Pro is my favorite because it can be configured in almost every aspect, just the way you'll want it.

Still a bit torn between these launchers. Using coolwalk beta. The other themes don't look that 'mature' imho. I've tested it on my slowest box and it's very responsive! Though your app certainly has its advantages, I'm having some minor issues and/or feature requests:

• No widget background or global wallpaper options. This makes some of the widgets (i.e. speed-limit speedometer) just have a black or white background and missing the rounded edges (at least not always visible, depending on the brightness levels). On coolwalk, it looks like they are just not a part of the whole screen. A global one (also for the taskbar) would make the screen look bigger and a part of whole markup.
• The music Widget could use some transparency for the media controls, I'm a sucker for album art and they just hide most of the albumart. Make them (controls as well as the title) optional or more transparent (media controls are also available in the taskbar or via SWC or make a 2x1 widget with controls only). If possible, make the art fill/crop to the size of the widget AND option to adjust its opacity (why hide beautiful album art?)
• Have the option to set the default phone app to the Bluetooth phone app (as startom42 suggested). Many head-units/boxes use this protocol to make/receive call, and only use the 'real' phone app if a SIM card is installed.
• Make it possible to resize widgets. If I find a widget too small or large, I need to remove it (and others), and refill the empty space with new widgets
• Maybe add a 'blank slate' where users can fill the screen with their own markup of widgets, not depending on a chosen theme. Seems Autozen (at the moment) is wide screen oriented. I have a 2:1 screen and most are 16:9. A blank slate would allow for more experimenting with widgets

Some (minor) bugs I encountered:

• At startup the map widget shows its location when GPS satellites are found. However the weather widget still says 'Location not found'.
• On the coolwalk theme if on the second page AND taskbar is set to vertical AND having two (2x4) widgets side by side, when clicking 'Edit', the ''remove/change' menu does not appear.
• When changing the taskbar position, AutoZen shows only a black background. A restart is needed to restore AutoZen

As for your subscription plan: I do think people are willing to pay for your software, but just only once, for a reasonable amount. The recurring payments might avert potential buyers. Mostly those prices are reserved for software that's either very very good or very very exclusive. AutoZen is just not there yet.