This is great news btw! Sorry, haven't been following the progress but it sounds all good. Are you using PWM's to control the brightness? If so, is it the same typical rate, ~15K?
Have you considered or looked at external temp sensor support? Are you having the same issue of I/O pin shortages or have you looked at I/O pin sharing as Mike C has done? I really think for us to take the next step, we need to look at the 16 KB Atmel with greater I/O pin counts - this would solve a bunch of road blocks I'm having. We just need to team up with a board designer and come up with an easy way to dnld the firmware to one of these MCU's. Couple options there - not difficult to do, takes some extra real estate, but we also save real estate because of the smaller foot print of these MCU's, if we go with the square 5x5x5x5 configuration.
From this chart: https://en.wikipedia.org/wiki/Atmel_AVR_ATtiny_comparison_chart
best option seems to be the 1634, pricing/package options here: https://www.arrow.com/en/products/search?q=attiny1634