We've been asking for multiple intermediate levels for starting tech for a long time. Just another of the gazillion changes we'd like to see...
For now, you can change the "Medium" level to be what you want, it's just not changeable IN the game, you have to edit the techarea text file. And, it's only ONE customizable option, so you have to edit each time you want something different.
In techarea.txt, the "Raise Level" setting is the level of this tech you will get if you choose "medium" for starting tech. It's that simple. But, it's up to you to make certain that the arrangement of these techs makes sense. Prerequsites are not checked.