[Nitram Draw]

MD,
I also usually play with those same self imposed restrictions and I also never capture another planet, unless I'm trying the Pirate trait. I always seem to get another colonization tech if I capture another planet. It does take something away from the game though.
I wonder if the 3 colonizing techs could be treated like a racial trait, if you didn't choose it in the beginning you can never learn it. Then you could capture enemy planets but not gain the tech.