I’m in the same position - designing whole home lighting from scratch.
I’ve still not got my head around the difference between DALI and KNX and why I’d do either, hence I find this discussion interesting. I don’t think you’ve got a conclusive answer yet
Same, it’s hard to get pricing for these components, also I’d add that, unless you are very familiar with the systems, it’s really hard to know what equipment you’d need to make a system. I have looked through so many DALI and KNX products and to be honest I’m confused by it
The above, as well as pricing, has led me towards DMX. I know it’s a very old standard, and mainly used in theatres etc, but from what I can tell it’s excellent in the home. You can control anything, the idea of RGB can be extended to RGBW, and then even to RGBCCWW, etc. You can pick up 12 channel actuators and run them from a central location for very low cost second hand, because of the very active market in commercial / stage DMX. For example I purchased a high quality 12 channel, 4A per channel dimming unit for £120. That’s £10 per channel, including nicely designed triacs and low EMF noise. You can’t beat it.
Also I have made an MQTT to DMX interface from a £5 Arduino. In my experience the Arduino is as reliable as its power supply (my test rig has been running constantly for years) but at this price you could buy 5 and keep them as backups.
The only sticking point for me is running LOTS of thick mains cable back to central location. I’d be much happier running thinner data cable back, and wiring the mains using ring circuits.
Like you said, why can’t you do this with KNX directly?
The flip side to this is that, at least I can easily access the dimmers when they overheat / break / need changing etc. I don’t like the idea of drivers in the ceiling voids or behind walls, because I just KNOW when you have 50 in the house, they will break often and need to take ceiling down. My parents house is littered with old transformers that never got replaced from the 1980s, and lights that just don’t work OR make a loud humming noise in the ceiling! So maybe running lots of thick cable back is not too bad.