Sounds like you've been busy! Weather + SQM is obviously super helpful (if you're looking for a rain sensor I love the RG-11 -
oceancontrols.com.au/hys-001.html) and of all the INDI-open-source hardware projects, it's the most robust IMHO. The other project that works great is the Arduino Flip-flat/Flatman clone - but I've not tried it with a flap for darks (with a truss Ritchey- Chretien the flap doesn't help much ;-) YMMV
Focus controllers is another area that's super confusing - soooo many options, not all of them well through through. The best I've found so far is Robert Brown's Arduino ASCOM Focuser Pro - it shouldn't be labeled as ASCOM as it appears to INDI as a Moonlite so it's great!
sourceforge.net/projects/arduinofocuscontrollerpro/
One of the other things buzzing around my head is adding Bonjour and Wifi/Ethernet (PoE) support for all these little devices both into the Arduino source code (there's a great Bonjour library for Arduino that makes the first part easy) but then re-writing all the INDI drivers for hardware to enable network support so that you can more easily add all these devices to your observatory without running bloody USB cables everywhere) - it's a dream but again if you look at what Wolfgang built with WeatherRadio it's not a crazy dream.
In my ideal world: focuser, flats, weather, power/switching and sensors can all be network connected to INDI and "findable" by Bonjour names (so no more hosts.txt or hard coded IP addresses) and ideally some way of mixing and matching the sensors you are interested in into the dashboards/tabs in EKOS eg: for temperature use the sensor on the focuser if there's no other temp sensor available, for cloud cover use the SQM with a weighting factor as a proxy, etc) - I have a feeling this might need to be a standalone server that consolidates all the sensors and dispatches all the commands, possibly linked to Watchdog for shutdown, but the less complexity the better.