KNX over Powerline is NOT slow, but it is about 30-50% more expensive than KNX over TP. Also, I do not know of any KNX over Powerline computer gateway that is supported. You can always add a KNX over Powerline to KNX over TP gateway, plus a KNX/IP gateway, but that adds around 600-700EUR to the equation.
If your electrician says you are too far into the building phase, fire him, and get a better electrician.
I wish I could fire him. But he is "bundled" with the house I'm building. I will do alot of work myself on low-power devieces. And are considering putting out a bus also, and putting pipes for wiring from different places to my technical room. That way, he can do what he have to do, and later I can do what I want to do!
But, I'm working on a solution.
If I'm going to put in the bus mysekf, the walls are not yet closed. You are taking about KNX over TP, TP=Twisted Pair?, is that just networking cable? Is it just to put this cable running allover my house, and make some boxes where i in the future wants some switches or sensors?
And then from my roof dimmers, just a pipe down to the techical room, so that I can dim/switch?