Hi,
1. We won't change that.
The unknown selection should work fine with UTF-8 CSV files and thus there is no need to change the default selection for you.
Actually, thanks to your message, I've tested it and found out that the unkown charset selection didn't work properly anymore and that you had to select the charset for the import to work properly.
I've added a patch on our end for the next release so that it works properly.
So when you update, you won't have to change the selection anymore.
2. We can't do that.
It's a technical restriction because otherwise, in the routing system of Joomla we can't separate some product URLs from category URLs if both SEF names are empty and thus you would end up with non working links.