when I'm playing custom games I tend to build obstructions generally, and add nations in after spawn to break up the big blobs in Russia and china regions.
But I agree. The Randomization stuff needs improvements. I'd prefer it if there were more options for random generation;
* small vs large states options (on region).
* HRE yes or no, and can change the HRE start provinces.
* religions in regions (would like option for Norse + more tengri random nations for example)
* Random province values to have an option where the development was random, but within predetermined ranges (e.g. higher in europe, lower in america etc.) similar to normal game, but with shuffled specifics.
As well as an option to make nations have the unit graphics not randomly generated, so that Europe isn't full of Japanese and Aztec castles, Muslim soldiers and Native American cities when they're all western tech.